It tells me that it can't convert int to bool.
Tried TryParse but for some reason the argument list is invalid.
Code:
private void SetNumber(string n)
{
// if user input is a number then
if (int.Parse(n))
{
// if user input is negative
if (h < 0)
{
// assign absolute version of user input
number = Math.Abs(n);
}
else
{
// else assign user input
number = n;
}
}
else
{
number = 0; // if user input is not an int then set number to 0
}
}
You were probably very close using TryParse, but I'm guessing you forgot the out keyword on the parameter:
int value;
if (int.TryParse(n, out value))
{
}
Just use this:
int i;
bool success = int.TryParse(n, out i);
if the parse was successful, success is true.
If that case i contain the number.
You probably got the out argument modifier wrong before. It has the out modifier to indicate that it is a value that gets initialized within the method called.
You can try with some simple regular expression :
bool IsNumber(string text)
{
Regex regex = new Regex(#"^[-+]?[0-9]*\.?[0-9]+$");
return regex.IsMatch(text);
}
private void SetNumber(string n)
{
int nVal = 0;
if (int.TryParse(n, out nVal))
{
if (nVal < 0)
number = Math.Abs(nVal);
else
number = nVal;
}
else
number = 0;
}
There are a lot of problems with this code:
Using VB-style line comments (') instead of C# slashes
Parse for integer returns an int and not a bool
You should use TryParse with an out value
h does not seem to be valid at all. Is it a type for n?
There are variables that do not seem to be defined in function scope (number) are they defined at class scope?
But try this:
private void SetNumber(string n)
{
int myInt;
if (int.TryParse(n, out myInt)) //if user input is a number then
{
if (myInt < 0) //if user input is negative
number = Math.Abs(n); //assign absolute version of user input
else //else assign user input
number = n;
}
else number = 0; //if user input is not an int then set number to 0
}
You could try something like below using int.TryParse..
private void SetNumber(string n)
{
int parsed = -1;
if (int.TryParse(n, out parsed)) //if user input is a number then
...
The reason there are complaints that it cannot convert an int to a bool is because the return type of int.Parse() is an int and not a bool and in c# conditionals need to evaluate bool values.
int.Parse will give you back an integer rather than a boolean.
You could use int.TryParse as you suggested.
int parsedValue;
if(int.TryParse(n, out parsedValue))
{
}
Well for one thing the inner if statement has an 'h' instead of an 'n' if(h < 0). But TryParse should work there assuming that 'number' is a class variable.
private void SetNumber(string n)
{
int temp;
bool success = Int32.TryParse(n, out temp);
// If conversion successful
if (success)
{
// If user input is negative
if (temp < 0)
number = Math.Abs(temp); // Assign absolute version of user input
else // Assign user input
number = temp;
}
else
{
number = 0;
}
}
int.Parse will convert a string to an integer. Current you have it within an if statement, so its treating the returned value of int.Parse as a bool, which its not.
Something like this will work:
private void SetNumber(string n)
{
int num = 0;
try{
num = int.Parse(n);
number = Math.Abs(num);
}catch(Exception e){
number = 0;
}
}
I did this in the simplest way I knew how.
static void Main(string[] args)
{
string a, b;
int f1, f2, x, y;
Console.WriteLine("Enter two inputs");
a = Convert.ToString(Console.ReadLine());
b = Console.ReadLine();
f1 = find(a);
f2 = find(b);
if (f1 == 0 && f2 == 0)
{
x = Convert.ToInt32(a);
y = Convert.ToInt32(b);
Console.WriteLine("Two inputs r number \n so tha additon of these text box is= " + (x + y).ToString());
}
else
Console.WriteLine("One or tho inputs r string \n so tha concadination of these text box is = " + (a + b));
Console.ReadKey();
}
static int find(string s)
{
string s1 = "";
int f;
for (int i = 0; i < s.Length; i++)
for (int j = 0; j <= 9; j++)
{
string c = j.ToString();
if (c[0] == s[i])
{
s1 += c[0];
}
}
if (s==s1)
f= 0;
else
f= 1;
return f;
}
Related
My goal is to make a math expression interpreter with c#, for example if you type "A=3", it'll save the A as a dictionary key and 3 as its value, this program has more features so if you type "B=3" and then "A=B+3" and then "Show(A)", it must display "6" as the answer.
Everything is right until I type something like "A=10" "B=10" "C=A+B" and finally "Show(C)", because Variables' value are 2-digit (or more) numbers in this case, when producing the final result, numbers are saved in the string like "01+01" instead of "10+10" (because A and B values are 10 so A+B should be 10+10), so it's kinda reversed.
I tried to reverse the string and then evaluate the answer but that didn't work as well, simply it gives me "1+1" for some reason!
Notes:
expression evaluation is done by "return Convert.ToInt32(new DataTable().Compute(result, null));"
because strings are immutable in c#, when every expression like "A+B" or "3+5" comes in the method, I create a new empty string like (string result = " ";) and then with the help of "result = ValidExpression[i] + result.Remove(counter, 0);", I change the variables with values (note = if all the elements of input are numbers, answer is right) like "A" with "23" and put them in the new string and then evaluate the final string. But as I said, it saves the 23 as 32 so the answer will be wrong.
This is my code and the bug is probably in the LongProcessing method.
Thanks for your helps.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Globalization;
using System.Data;
namespace ConsoleApp2
{
class Program
{
static void Main(string[] args)
{
Console.WriteLine("Welcome To The Program\nCorrect Syntax:");
Console.WriteLine("A=10\nB=15\nC=A+B\nD=13/4-2+A-C+B\nShow(D)");
Console.WriteLine("\nEnter your input:");
Expression E = new Expression();
string expression = "start";
while (expression != "exit")
{
expression = Console.ReadLine();
// for show command
if (expression.Contains("Show") == true)
try { E.Show(expression[5]); }
catch (Exception e)
{
Console.WriteLine("input is not correct, Can not show anything. please try again");
}
if (E.Validation(expression) == false)
Console.WriteLine("input is not correct, please try again");
else
E.Processing(expression);
}
Console.ReadKey();
}
}
class Expression
{
public Dictionary<Char, String> Variables = new Dictionary<Char, String>();
public Expression()
{ }
public Boolean Validation(string expression)
{
// true if c is a letter or a decimal digit; otherwise, false && true if c is a decimal digit; otherwise, false.
if (!Char.IsLetterOrDigit(expression[0]) || Char.IsDigit(expression[0]))
return false;
else
return true;
}
public void Processing(String ValidExpression)
{
// Update Dictionary with new values per key
if (Variables.ContainsKey(ValidExpression[0]))
Variables.Remove(ValidExpression[0]);
string temp = " ";
if (ValidExpression.Length > 2 && !ValidExpression.Contains("Show") && !ValidExpression.Contains("exit"))
{
// removing the variable name and "=" from the string
for (int i = 2; i < ValidExpression.Length; i++)
temp = ValidExpression[i] + temp.Remove(i, 0);
Variables.Add(ValidExpression[0], LongProcessing(temp).ToString());
}
}
// something is wrong in this method
public int LongProcessing(String ValidExpression)
{
string temp;
int counter = 0;
string result = " ";
for (int i = 0; i < ValidExpression.Length; i++)
{
//changing variables (letters) with values
if (Char.IsLetter(ValidExpression[i]))
{
if (Variables.ContainsKey(ValidExpression[i]))
{
Variables.TryGetValue(ValidExpression[i], out temp);
for (int j = 0; j < temp.Length; j++)
{
result = temp[j] + result.Remove(counter, 0);
counter++;
}
}
}
else
{
result = ValidExpression[i] + result.Remove(counter, 0);
counter++;
}
}
// checks if all of the string elements are numbers
if (ValidExpression.All(char.IsDigit))
return Convert.ToInt32(ValidExpression);
else
{
return Convert.ToInt32(new DataTable().Compute(result, null));
}
}
public void Show(Char ValidExpression)
{
Console.WriteLine(Variables[ValidExpression]);
}
}
}
This is broken:
for (int i = 2; i < ValidExpression.Length; i++)
temp = ValidExpression[i] + temp.Remove(i, 0);
temp.Remove(i, 0) is a non op, you might as well just write temp
So let's plot the loop:
Assume ValidExpression is "A=10"
Temp starts out as " "
First iteration, temp is "1 "
Second iteration, temp is "01 "
Any operation that works left to right through a string, character by character, pulling a character out and sticking it on the start of a growing string, will reverse the string
Perhaps you meant to not have a loop and instead do temp = ValidExpression.Substring(2) ?
Here are some suggestions:
Start by looking at the value of "temp" in "Processing". To assist in your debugging, add a "Console.WriteLine" statement.
public void Processing(String ValidExpression)
{
// Update Dictionary with new values per key
if (Variables.ContainsKey(ValidExpression[0]))
Variables.Remove(ValidExpression[0]);
string temp = " ";
if (ValidExpression.Length > 2 && !ValidExpression.Contains("Show") && !ValidExpression.Contains("exit"))
{
// removing the variable name and "=" from the string
for (int i = 2; i < ValidExpression.Length; i++)
{
temp = ValidExpression[i] + temp.Remove(i, 0);
Console.WriteLine(" temp: " + temp); //added for debugging
}
Variables.Add(ValidExpression[0], LongProcessing(temp).ToString());
}
}
A couple of other things:
The user is never informed how to exit.
There is a class named "Expression" and a string variable named
"expression". This is likely to cause confusion.
You may also want to look at this post: how to convert a string to a mathematical expression programmatically
So I have a text box and on the text changed event I have the old text and the new text, and want to get the difference between them. In this case, I want to be able to recreate the new text with the old text using one remove function and one insert function. That is possible because there are a few possibilities of the change that was in the text box:
Text was only removed (one character or more using selection) - ABCD -> AD
Text was only added (one character or more using paste) - ABCD -> ABXXCD
Text was removed and added (by selecting text and entering text in the same action) - ABCD -> AXD
So I want to have these functions:
Sequence GetRemovedCharacters(string oldText, string newText)
{
}
Sequence GetAddedCharacters(string oldText, string newText)
{
}
My Sequence class:
public class Sequence
{
private int start;
private int end;
public Sequence(int start, int end)
{
StartIndex = start; EndIndex = end;
}
public int StartIndex { get { return start; } set { start = value; Length = end - start + 1; } }
public int EndIndex { get { return end; } set { end = value; Length = end - start + 1; } }
public int Length { get; private set; }
public override string ToString()
{
return "(" + StartIndex + ", " + EndIndex + ")";
}
public static bool operator ==(Sequence a, Sequence b)
{
if(IsNull(a) && IsNull(b))
return true;
else if(IsNull(a) || IsNull(b))
return false;
else
return a.StartIndex == b.StartIndex && a.EndIndex == b.EndIndex;
}
public override bool Equals(object obj)
{
return base.Equals(obj);
}
public static bool operator !=(Sequence a, Sequence b)
{
if(IsNull(a) && IsNull(b))
return false;
else if(IsNull(a) || IsNull(b))
return true;
else
return a.StartIndex != b.StartIndex && a.EndIndex != b.EndIndex;
}
public override int GetHashCode()
{
return base.GetHashCode();
}
static bool IsNull(Sequence sequence)
{
try
{
return sequence.Equals(null);
}
catch(NullReferenceException)
{
return true;
}
}
}
Extra Explanation: I want to know which characters were removed and which characters were added to the text in order to get the new text so I can recreate this. Let's say I have ABCD -> AXD. 'B' and 'C' would be the characters that were removed and 'X' would be the character that was added. So the output from the GetRemovedCharacters function would be (1, 2) and the output from the GetAddedCharacters function would be (1, 1). The output from the GetRemovedCharacters function refers to indexes in the old text and the output from the GetAddedCharacters function refers to indexes in the old text after removing the removed characters.
EDIT: I've thought of a few directions:
This code I created* which returns the sequence that was affected - if characters were removed it returns the sequence of the characters that were removed in the old text; if characters were added it returns the sequence of the characters that were added in the new text. It does not return the right value (which I myself not sure what I want it to be) when removing and adding text.
Maybe the SelectionStart property in the text box could help - the position of the caret after the text was changed.
*
private static Sequence GetChangeSequence(string oldText, string newText)
{
if(newText.Length > oldText.Length)
{
for(int i = 0; i < newText.Length; i++)
if(i == oldText.Length || newText[i] != oldText[i])
return new Sequence(i, i + (newText.Length - oldText.Length) - 1);
return null;
}
else if(newText.Length < oldText.Length)
{
for(int i = 0; i < oldText.Length; i++)
if(i == newText.Length || oldText[i] != newText[i])
return new Sequence(i, i + (oldText.Length - newText.Length) - 1);
return null;
}
else
return null;
}
Thanks.
A simple string comparison wont do the job since you are asking for a algorithm which supports added and removed chars at the same time and is hence not easy to achive in a few lines of code. Id suggest to use a library instead of writing your own comparison algorithm.
Have a look at this project for example.
I quickly threw this together to give you an idea of what I did to solve your question. It doesn't use your classes but it does find an index so it's customizable for you.
There are also obvious limitations to this as it is just bare bones.
This method will spot out changes made to the original string by comparing it to the changed string
// Find the changes made to a string
string StringDiff (string originalString, string changedString)
{
string diffString = "";
// Iterate over the original string
for (int i = 0; i < originalString.Length; i++)
{
// Get the character to search with
char diffChar = originalString[i];
// If found char in the changed string
if (FindInString(diffChar, changedString, out int index))
{
// Remove from the changed string at the index as we don't want to match to this char again
changedString = changedString.Remove(index, 1);
}
// If not found then this is a difference
else
{
// Add to diff string
diffString += diffChar;
}
}
return diffString;
}
This method will return true at the first matching occurrence (an obvious limitation but this is more to give you an idea)
// Find char at first occurence in string
bool FindInString (char c, string search, out int index)
{
index = -1;
// Iterate over search string
for (int i = 0; i < search.Length; i++)
{
// If found then return true with index
if (c == search[i])
{
index = i;
return true;
}
}
return false;
}
This is a simple helper method to show you an example
void SplitStrings(string oldStr, string newStr)
{
Console.WriteLine($"Old : {oldStr}, New: {newStr}");
Console.WriteLine("Removed - " + StringDiff(oldStr, newStr));
Console.WriteLine("Added - " + StringDiff(newStr, oldStr));
}
I've done it.
static void Main(string[] args)
{
while(true)
{
Console.WriteLine("Enter the Old Text");
string oldText = Console.ReadLine();
Console.WriteLine("Enter the New Text");
string newText = Console.ReadLine();
Console.WriteLine("Enter the Caret Position");
int caretPos = int.Parse(Console.ReadLine());
Sequence removed = GetRemovedCharacters(oldText, newText, caretPos);
if(removed != null)
oldText = oldText.Remove(removed.StartIndex, removed.Length);
Sequence added = GetAddedCharacters(oldText, newText, caretPos);
if(added != null)
oldText = oldText.Insert(added.StartIndex, newText.Substring(added.StartIndex, added.Length));
Console.WriteLine("Worked: " + (oldText == newText).ToString());
Console.ReadKey();
Console.Clear();
}
}
static Sequence GetRemovedCharacters(string oldText, string newText, int caretPosition)
{
int startIndex = GetStartIndex(oldText, newText);
if(startIndex != -1)
{
Sequence sequence = new Sequence(startIndex, caretPosition + (oldText.Length - newText.Length) - 1);
if(SequenceValid(sequence))
return sequence;
}
return null;
}
static Sequence GetAddedCharacters(string oldText, string newText, int caretPosition)
{
int startIndex = GetStartIndex(oldText, newText);
if(startIndex != -1)
{
Sequence sequence = new Sequence(GetStartIndex(oldText, newText), caretPosition - 1);
if(SequenceValid(sequence))
return sequence;
}
return null;
}
static int GetStartIndex(string oldText, string newText)
{
for(int i = 0; i < Math.Max(oldText.Length, newText.Length); i++)
if(i >= oldText.Length || i >= newText.Length || oldText[i] != newText[i])
return i;
return -1;
}
static bool SequenceValid(Sequence sequence)
{
return sequence.StartIndex >= 0 && sequence.EndIndex >= 0 && sequence.EndIndex >= sequence.StartIndex;
}
I'd like to know on C# how to check if a string is a number (and just a number).
Example :
141241 Yes
232a23 No
12412a No
and so on...
Is there a specific function?
Look up double.TryParse() if you're talking about numbers like 1, -2 and 3.14159. Some others are suggesting int.TryParse(), but that will fail on decimals.
string candidate = "3.14159";
if (double.TryParse(candidate, out var parsedNumber))
{
// parsedNumber is a valid number!
}
EDIT: As Lukasz points out below, we should be mindful of the thread culture when parsing numbers with a decimal separator, i.e. do this to be safe:
double.TryParse(candidate, NumberStyles.AllowDecimalPoint, CultureInfo.InvariantCulture, out var parsedNumber)
If you just want to check if a string is all digits (without being within a particular number range) you can use:
string test = "123";
bool allDigits = test.All(char.IsDigit);
Yes there is
int temp;
int.TryParse("141241", out temp) = true
int.TryParse("232a23", out temp) = false
int.TryParse("12412a", out temp) = false
Hope this helps.
Use Int32.TryParse()
int num;
bool isNum = Int32.TryParse("[string to test]", out num);
if (isNum)
{
//Is a Number
}
else
{
//Not a number
}
MSDN Reference
Use int.TryParse():
string input = "141241";
int ouput;
bool result = int.TryParse(input, out output);
result will be true if it was.
Yep - you can use the Visual Basic one in C#.It's all .NET; the VB functions IsNumeric, IsDate, etc are actually static methods of the Information class. So here's your code:
using Microsoft.VisualBasic;
...
Information.IsNumeric( object );
int value;
if (int.TryParse("your string", out value))
{
Console.WriteLine(value);
}
This is my personal favorite
private static bool IsItOnlyNumbers(string searchString)
{
return !String.IsNullOrEmpty(searchString) && searchString.All(char.IsDigit);
}
Perhaps you're looking for the int.TryParse function.
http://msdn.microsoft.com/en-us/library/system.int32.tryparse.aspx
Many datatypes have a TryParse-method that will return true if it managed to successfully convert to that specific type, with the parsed value as an out-parameter.
In your case these might be of interest:
http://msdn.microsoft.com/en-us/library/system.int32.tryparse.aspx
http://msdn.microsoft.com/en-us/library/system.decimal.tryparse.aspx
int result = 0;
bool isValidInt = int.TryParse("1234", out result);
//isValidInt should be true
//result is the integer 1234
Of course, you can check against other number types, like decimal or double.
You should use the TryParse method for the int
string text1 = "x";
int num1;
bool res = int.TryParse(text1, out num1);
if (res == false)
{
// String is not a number.
}
If you want to validate if each character is a digit and also return the character that is not a digit as part of the error message validation, then you can loop through each char.
string num = "123x";
foreach (char c in num.ToArray())
{
if (!Char.IsDigit(c))
{
Console.WriteLine("character " + c + " is not a number");
return;
}
}
int.TryPasrse() Methode is the best way
so if the value was string you will never have an exception , instead of the TryParse Methode return to you bool value so you will know if the parse operation succeeded or failed
string yourText = "2";
int num;
bool res = int.TryParse(yourText, out num);
if (res == true)
{
// the operation succeeded and you got the number in num parameter
}
else
{
// the operation failed
}
string str = "123";
int i = Int.Parse(str);
If str is a valid integer string then it will be converted to integer and stored in i other wise Exception occur.
Starting with C# 7.0, you can declare the out variable in the argument
list of the method call, rather than in a separate variable
declaration. This produces more compact, readable code, and also
prevents you from inadvertently assigning a value to the variable
before the method call.
bool isDouble = double.TryParse(yourString, out double result);
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/out-parameter-modifier
You could use something like the following code:
string numbers = "numbers you want to check";
Regex regex = new Regex("^[0-9]+$"));
if (regex.IsMatch(numbers))
{
//string value is a number
}
public static void Main()
{
string id = "141241";
string id1 = "232a23";
string id2 = "12412a";
validation( id, id1, id2);
}
public static void validation(params object[] list)
{
string s = "";
int result;
string _Msg = "";
for (int i = 0; i < list.Length; i++)
{
s = (list[i].ToString());
if (string.IsNullOrEmpty(s))
{
_Msg = "Please Enter the value";
}
if (int.TryParse(s, out result))
{
_Msg = "Enter " + s.ToString() + ", value is Integer";
}
else
{
_Msg = "This is not Integer value ";
}
}
}
Try This
here i perform addition of no and concatenation of string
private void button1_Click(object sender, EventArgs e)
{
bool chk,chk1;
int chkq;
chk = int.TryParse(textBox1.Text, out chkq);
chk1 = int.TryParse(textBox2.Text, out chkq);
if (chk1 && chk)
{
double a = Convert.ToDouble(textBox1.Text);
double b = Convert.ToDouble(textBox2.Text);
double c = a + b;
textBox3.Text = Convert.ToString(c);
}
else
{
string f, d,s;
f = textBox1.Text;
d = textBox2.Text;
s = f + d;
textBox3.Text = s;
}
}
I'm not a programmer of particularly high skills, but when I needed to solve this, I chose what is probably a very non-elegant solution, but it suits my needs.
private bool IsValidNumber(string _checkString, string _checkType)
{
float _checkF;
int _checkI;
bool _result = false;
switch (_checkType)
{
case "int":
_result = int.TryParse(_checkString, out _checkI);
break;
case "float":
_result = Single.TryParse(_checkString, out _checkF);
break;
}
return _result;
}
I simply call this with something like:
if (IsValidNumber("1.2", "float")) etc...
It means that I can get a simple true/false answer back during If... Then comparisons, and that was the important factor for me. If I need to check for other types, then I add a variable, and a case statement as required.
use this
double num;
string candidate = "1";
if (double.TryParse(candidate, out num))
{
// It's a number!
}
int num;
bool isNumeric = int.TryParse("123", out num);
namespace Exception
{
class Program
{
static void Main(string[] args)
{
bool isNumeric;
int n;
do
{
Console.Write("Enter a number:");
isNumeric = int.TryParse(Console.ReadLine(), out n);
} while (isNumeric == false);
Console.WriteLine("Thanks for entering number" + n);
Console.Read();
}
}
}
Regex.IsMatch(stringToBeChecked, #"^\d+$")
Regex.IsMatch("141241", #"^\d+$") // True
Regex.IsMatch("232a23", #"^\d+$") // False
Regex.IsMatch("12412a", #"^\d+$") // False
The problem with some of the suggested solutions is that they don't take into account various float number formats. The following function does it:
public bool IsNumber(String value)
{
double d;
if (string.IsNullOrWhiteSpace(value))
return false;
else
return double.TryParse(value.Trim(), System.Globalization.NumberStyles.Any,
System.Globalization.CultureInfo.InvariantCulture, out d);
}
It assumes that the various float number styles such es decimal point (English) and decima comma (German) are all allowed. If that is not the case, change the number styles paramater. Note that Any does not include hex mumbers, because the type double does not support it.
if i have this string:
12345 = true
123a45 = false
abcde = false
how to do it in C#?
Regex.IsMatch(sinput,#"\d+");
to match a string containing just digits.
If you forgot an optional digit in the question,
use this:
Regex.IsMatch("+12345", #"[+-]?\d+");
If you want to avoid RegEx, then you can use the built-in char methods:
bool allDigits = s.All(c => char.IsDigit(c));
This is the code for checking only letters in string in C#. You can modify it upto your need.
using System;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string MyString = "A #string & and 2.";
Console.WriteLine(MyString);
for (int charpos = 0; charpos < MyString.Length; charpos++)
{
Console.WriteLine(Char.IsLetter(MyString, charpos));
}
//Keep the console on screen
Console.WriteLine("Press any key to quit.");
Console.ReadKey();
}
}
}
private bool ContainsText(string input)
{
for (int i = 0; i < input.Length; i++)
{
if (((int) input[i] >= 65 && (int) input[i] <= 90) || ((int) input[i] >= 97 && (int) input[i] <= 177))
return true;
}
return false;
}
Running:
MessageBox.Show(ContainsText("abc").ToString());
MessageBox.Show(ContainsText("123").ToString());
MessageBox.Show(ContainsText("123b23").ToString());
returns True, False, True respectively
int myNumber;
if( int.TryParse(myString, out myNumber) == true )
{
// is a number and myNumber contains it
}
else
{
// isn't a number
}
if it's a BIG number, use long or double or.... instead of int.
int.TryParse or long.TryParse.
You can also use Regex for any length of number:
if (Regex.IsMatch(str, "^[0-9]+$"))
// ...
The question is complicated but I will explain it in details.
The goal is to make a function which will return next "step" of the given string.
For example
String.Step("a"); // = "b"
String.Step("b"); // = "c"
String.Step("g"); // = "h"
String.Step("z"); // = "A"
String.Step("A"); // = "B"
String.Step("B"); // = "C"
String.Step("G"); // = "H"
Until here its quite easy, But taking in mind that input IS string it can contain more than 1 characters and the function must behave like this.
String.Step("Z"); // = "aa";
String.Step("aa"); // = "ab";
String.Step("ag"); // = "ah";
String.Step("az"); // = "aA";
String.Step("aA"); // = "aB";
String.Step("aZ"); // = "ba";
String.Step("ZZ"); // = "aaa";
and so on...
This doesn't exactly need to extend the base String class.
I tried to work it out by each characters ASCII values but got stuck with strings containing 2 characters.
I would really appreciate if someone can provide full code of the function.
Thanks in advance.
EDIT
*I'm sorry I forgot to mention earlier that the function "reparse" the self generated string when its length reaches n.
continuation of this function will be smth like this. for example n = 3
String.Step("aaa"); // = "aab";
String.Step("aaZ"); // = "aba";
String.Step("aba"); // = "abb";
String.Step("abb"); // = "abc";
String.Step("abZ"); // = "aca";
.....
String.Step("zzZ"); // = "zAa";
String.Step("zAa"); // = "zAb";
........
I'm sorry I didn't mention it earlier, after reading some answers I realised that the problem was in question.
Without this the function will always produce character "a" n times after the end of the step.
NOTE: This answer is incorrect, as "aa" should follow after "Z"... (see comments below)
Here is an algorithm that might work:
each "string" represents a number to a given base (here: twice the count of letters in the alphabet).
The next step can thus be computed by parsing the "number"-string back into a int, adding 1 and then formatting it back to the base.
Example:
"a" == 1 -> step("a") == step(1) == 1 + 1 == 2 == "b"
Now your problem is reduced to parsing the string as a number to a given base and reformatting it. A quick googling suggests this page: http://everything2.com/title/convert+any+number+to+decimal
How to implement this?
a lookup table for letters to their corresponding number: a=1, b=2, c=3, ... Y = ?, Z = 0
to parse a string to number, read the characters in reverse order, looking up the numbers and adding them up:
"ab" -> 2*BASE^0 + 1*BASE^1
with BASE being the number of "digits" (2 count of letters in alphabet, is that 48?)
EDIT: This link looks even more promising: http://www.citidel.org/bitstream/10117/20/12/convexp.html
Quite collection of approaches, here is mine:-
The Function:
private static string IncrementString(string s)
{
byte[] vals = System.Text.Encoding.ASCII.GetBytes(s);
for (var i = vals.Length - 1; i >= 0; i--)
{
if (vals[i] < 90)
{
vals[i] += 1;
break;
}
if (vals[i] == 90)
{
if (i != 0)
{
vals[i] = 97;
continue;
}
else
{
return new String('a', vals.Length + 1);
}
}
if (vals[i] < 122)
{
vals[i] += 1;
break;
}
vals[i] = 65;
break;
}
return System.Text.Encoding.ASCII.GetString(vals);
}
The Tests
Console.WriteLine(IncrementString("a") == "b");
Console.WriteLine(IncrementString("z") == "A");
Console.WriteLine(IncrementString("Z") == "aa");
Console.WriteLine(IncrementString("aa") == "ab");
Console.WriteLine(IncrementString("az") == "aA");
Console.WriteLine(IncrementString("aZ") == "ba");
Console.WriteLine(IncrementString("zZ") == "Aa");
Console.WriteLine(IncrementString("Za") == "Zb");
Console.WriteLine(IncrementString("ZZ") == "aaa");
public static class StringStep
{
public static string Next(string str)
{
string result = String.Empty;
int index = str.Length - 1;
bool carry;
do
{
result = Increment(str[index--], out carry) + result;
}
while (carry && index >= 0);
if (index >= 0) result = str.Substring(0, index+1) + result;
if (carry) result = "a" + result;
return result;
}
private static char Increment(char value, out bool carry)
{
carry = false;
if (value >= 'a' && value < 'z' || value >= 'A' && value < 'Z')
{
return (char)((int)value + 1);
}
if (value == 'z') return 'A';
if (value == 'Z')
{
carry = true;
return 'a';
}
throw new Exception(String.Format("Invalid character value: {0}", value));
}
}
Split the input string into columns and process each, right-to-left, like you would if it was basic arithmetic. Apply whatever code you've got that works with a single column to each column. When you get a Z, you 'increment' the next-left column using the same algorithm. If there's no next-left column, stick in an 'a'.
I'm sorry the question is stated partly.
I edited the question so that it meets the requirements, without the edit the function would end up with a n times by step by step increasing each word from lowercase a to uppercase z without "re-parsing" it.
Please consider re-reading the question, including the edited part
This is what I came up with. I'm not relying on ASCII int conversion, and am rather using an array of characters. This should do precisely what you're looking for.
public static string Step(this string s)
{
char[] stepChars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".ToCharArray();
char[] str = s.ToCharArray();
int idx = s.Length - 1;
char lastChar = str[idx];
for (int i=0; i<stepChars.Length; i++)
{
if (stepChars[i] == lastChar)
{
if (i == stepChars.Length - 1)
{
str[idx] = stepChars[0];
if (str.Length > 1)
{
string tmp = Step(new string(str.Take(str.Length - 1).ToArray()));
str = (tmp + str[idx]).ToCharArray();
}
else
str = new char[] { stepChars[0], str[idx] };
}
else
str[idx] = stepChars[i + 1];
break;
}
}
return new string(str);
}
This is a special case of a numeral system. It has the base of 52. If you write some parser and output logic you can do any kind of arithmetics an obviously the +1 (++) here.
The digits are "a"-"z" and "A" to "Z" where "a" is zero and "Z" is 51
So you have to write a parser who takes the string and builds an int or long from it. This function is called StringToInt() and is implemented straight forward (transform char to number (0..51) multiply with 52 and take the next char)
And you need the reverse function IntToString which is also implementet straight forward (modulo the int with 52 and transform result to digit, divide the int by 52 and repeat this until int is null)
With this functions you can do stuff like this:
IntToString( StringToInt("ZZ") +1 ) // Will be "aaa"
You need to account for A) the fact that capital letters have a lower decimal value in the Ascii table than lower case ones. B) The table is not continuous A-Z-a-z - there are characters inbetween Z and a.
public static string stepChar(string str)
{
return stepChar(str, str.Length - 1);
}
public static string stepChar(string str, int charPos)
{
return stepChar(Encoding.ASCII.GetBytes(str), charPos);
}
public static string stepChar(byte[] strBytes, int charPos)
{
//Escape case
if (charPos < 0)
{
//just prepend with a and return
return "a" + Encoding.ASCII.GetString(strBytes);
}
else
{
strBytes[charPos]++;
if (strBytes[charPos] == 91)
{
//Z -> a plus increment previous char
strBytes[charPos] = 97;
return stepChar(strBytes, charPos - 1); }
else
{
if (strBytes[charPos] == 123)
{
//z -> A
strBytes[charPos] = 65;
}
return Encoding.ASCII.GetString(strBytes);
}
}
}
You'll probably want some checking in place to ensure that the input string only contains chars A-Za-z
Edit Tidied up code and added new overload to remove redundant byte[] -> string -> byte[] conversion
Proof http://geekcubed.org/random/strIncr.png
This is a lot like how Excel columns would work if they were unbounded. You could change 52 to reference chars.Length for easier modification.
static class AlphaInt {
private static string chars =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static string StepNext(string input) {
return IntToAlpha(AlphaToInt(input) + 1);
}
public static string IntToAlpha(int num) {
if(num-- <= 0) return "a";
if(num % 52 == num) return chars.Substring(num, 1);
return IntToAlpha(num / 52) + IntToAlpha(num % 52 + 1);
}
public static int AlphaToInt(string str) {
int num = 0;
for(int i = 0; i < str.Length; i++) {
num += (chars.IndexOf(str.Substring(i, 1)) + 1)
* (int)Math.Pow(52, str.Length - i - 1);
}
return num;
}
}
LetterToNum should be be a Function that maps "a" to 0 and "Z" to 51.
NumToLetter the inverse.
long x = "aazeiZa".Aggregate((x,y) => (x*52) + LetterToNum(y)) + 1;
string s = "";
do { // assertion: x > 0
var c = x % 52;
s = NumToLetter() + s;
x = (x - c) / 52;
} while (x > 0)
// s now should contain the result