Develop Reference

Program that converts numbers to letters both ways

I'm working on a program that encodes and decodes letters to numbers. I have the Encoding properly built but the decoding is giving me problems. I'm using int to char conversions with the ASCII table as the key. It doesn't seem like the conversion logic for the decoding is right but I really have no idea how to fix it. This is my first time using this conversion method so I still don't fully understand it.
*edit This is on a windows form app that has three buttons and two text boxes. Encode is one button, and you type in a sentence and it outputs in in numbers for each letter. Decode is another but it does the opposite type in numbers and get words. the third button is clear so thats not important. Sorry I left this out of the initial question.
class LetterCodeLogic
{
public static string Encode(string msg)
{
string result = "";
string m = msg.ToUpper();
char c;
int x;
for(int i = 0; i < m.Length; i++)
{
c = Convert.ToChar(m[i]);
x = c;
if (x == 32)
{
x = 0;
}
else
{
x -= 64;
if (x < 1 || x > 26)
{
x = 99;
}
}
result += x.ToString() + " ";
}
return result;
}
public static string Decode(string msg)
{
string result = "";
string[] nums = msg.Split(',');
char c;
int x;
for (int i = 0; i < msg.Length; i++)
{
x = Convert.ToChar(msg[i]);
c = (char)x;
if (c == 0)
{
c = (char)32;
}
else
{
c -= (char)64;
if (c < 65 || c > 90)
{
c = (char)35;
}
}
result += c.ToString() + " ";
}
return result;
}
}

I find problems like this are far easier when you break them into parts. First, write functions that convert a single character to a number or vice versa.
static public byte Encode(char c)
{
if (c == ' ') return 0;
if (c >= 'A' && c <= 'Z') return (byte)(c - 'A' + 1);
return 99;
}
static public char Decode(byte n)
{
if (n == 0) return ' ';
if (n >= 1 && n <= 27) return (char)(n + 'A' - 1);
return '#';
}
Now the functions you need are very easy to write:
static public string Encode(string stringInput)
{
return string.Join(" ", stringInput.Select(Encode).Select( b => b.ToString() ));
}
static public string Decode(string numericInput)
{
return new string(numericInput.Split(' ').Select( n => byte.Parse(n)).Select(Decode).ToArray());
}

StringToASCII from scratch failed

I actually tried to make a StringToASCII function from scratch in c#.
I get the input from _myString and this is the code :
public void convertToASCII() {
//A-Z --> 65-90
//a-z --> 97-122
//0-9 --> 48-57
//Space --> 32
int[] returnString = new int[_myString.Length];
int iTableau = 0;
char iAZ = 'A';
char iaz = 'a';
char i09 = '0';
char iSpace = ' ';
for(int i = 0; i < _myString.Length; i++)
{
if(_myString[i] >= 65 && _myString[i] <= 90 || _myString[i] >= 97 && _myString[i] <= 122 || _myString[i] >= 48 && _myString[i] <= 57 || _myString[i] == 32)
{
while(iAZ < 90 || iaz < 122 || iaz < 122 || i09 < 57 || _myString[i] == 32)
{
if(_myString[i] == iAZ && iAZ >= 'A' && iAZ <= 'Z')
{
returnString[iTableau] = iAZ;
iTableau++;
iAZ--;
}
else
{
iAZ++;
}
if(_myString[i] == iaz && iaz >= 'a' && iaz <= 'z')
{
returnString[iTableau] = iaz;
iTableau++;
iaz--;
}
else
{
iaz++;
}
if(_myString[i] == i09 && i09 >= '0' && i09 <= '9')
{
returnString[iTableau] = i09;
iTableau++;
i09--;
}
else
{
i09++;
}
if(_myString[i] == iSpace)
{
returnString[iTableau] = iSpace;
iTableau++;
}
}
}
}
_myString = "";
for (int i = 0; i < returnString.Length; i++)
{
_myString += returnString[i];
}
}
I also tried this kind of function which it works, but i would like to make one who checks only chars from A-Z and a-z and 0-9 and space.
Same thing as the first function, i take the input from a global string variable called "_myString".
public void convertToASCII()
{
string asciiChar;
string returnString = "";
foreach (char c in _myString)
{
asciiChar= ((int)(c)).ToString();
returnString += " " + asciiChar;
}
_myString = returnString;
}

This is actually relatively simple:
public string StringToLettersOrNumbersOrSpace(string input)
{
var sb = new StringBuilder();
for (int i = 0; i < input.Length; i++)
{
if (Char.IsLetterOrDigit(input[i]) || input[i] == ' ')
{
sb.Append(input[i]);
}
}
return sb.ToString();
}
First, you'll want to use StringBuilder instead of continuously appending to a string variable. Strings in C# are immutable, meaning that they can't be changed after they've been created, so doing something like string s1 = "aaa"; s1 += "bbb"; will actually create an entirely new string instead of just adding to the original. StringBuilder, on the other hand, is mutable, so you don't need to worry about reallocating a bunch of strings every time you want to concatenate strings (which gets progressively slower and slower as the string gets bigger).
Second, you can use Char.IsLetterOrDigit instead of using comparisons. The method takes a char as input and returns true if the character is a letter (uppercase or lowercase) or a number. This maps directly to your desired range a-z, A-Z, and 0-9. Since you also care about spaces, though, you will have to manually check for that.

How to write a code for my decrypt without special character

I am only able to encrypt, but i do not how to decrypt. Someone please help. Do I have to declare a bool variable?
Or is that any other better way to do it?
string UserInput = "";
int shift;
Shift OBSHIFT = new Shift();
Console.Write("\nType a string to encrypt:");
UserInput = Console.ReadLine();
Console.Write("How many chars would you like to shift?: ");
shift = int.Parse(Console.ReadLine());
Console.WriteLine("\nApplying Caesar cipher ... ");
Console.Write("Your encrypted string is: ");
Console.WriteLine(OBSHIFT.Cshift(UserInput, shift));
Console.Read();
}
}
class Shift
{
public string Cshift(string str, int shift )
{
string UserOutput = "";
char[] A = null;
A = str.ToCharArray();
int temp;
for (int i = 0; i < str.Length; i++)
{
char c = A[i];
if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))
{
temp = (int)(A[i] + shift);
if ((c >= 'A' && c <= 'Z' && temp > 'Z') || (c >= 'a' && c <= 'z' && temp > 'z'))
temp = temp - 26;
else
temp = (int)(A[i] + (shift));
}
else
temp = c;
UserOutput += (char)temp;
}
return UserOutput;
}
}
}
}

Talking about Caesar cipher, you can simply negate the shift and get the original string.
I.e., cshift(cshift(string, x), -x) == string.
Using your Shift class:
int sh = 17;
string original = "abcdefgh";
string encrypted = shift.Cshift(original, sh);
string decrypted = shift.Cshift(shifted, -sh);
Console.WriteLine(decrypted == original); // true
For convenience, you can create a method Decrypt, which will do this:
class Shift
{
public string Encrypt(string originalString, int shift)
{
string userOutput = "";
char[] a = originalString.ToCharArray();
for (int i = 0; i < originalString.Length; i++)
{
char c = a[i];
int temp;
if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'))
{
temp = (int)(a[i] + shift);
if ((c >= 'A' && c <= 'Z' && temp > 'Z') || (c >= 'a' && c <= 'z' && temp > 'z'))
temp = temp - 26;
else
temp = (int)(a[i] + (shift));
}
else
temp = c;
userOutput += (char)temp;
}
return userOutput;
}
public string Decrypt(string cipherString, int shift)
{
return Encrypt(cipherString, -shift);
}
}
Note that I have also done some little code improvements like:
combined declaration and assignment of A
moved temp into the inner scope
gave the proper names to the local variables (lower-case)

Printing Reverse Triangle with Alphabets

I have to print the following pattern in C# -
A B C D E F G F E D C B A
A B C D E F E D C B A
A B C D E D C B A
A B C D C B A
A B C B A
A B A
A
I'm able to print the pattern in C but not in C# because the character input does not work in C#. I tried converting it but I'm not able to convert it properly and facing the problems with for loops. Please tell me how to write equivalent C# code.
Thanks in advance.
C code is:
#include<stdio.h>
#include<conio.h>
int main()
{
char ch,r,c;
int sp;
printf("\nEnter last character of triangle : ");
scanf("%c",&ch);
if(ch>='a' && ch<='z')
ch=ch-32;
printf("\n");
for(r='A'; 'A'<=ch; ch--,r++)
{
for(sp=r; sp>'A'; sp--)
printf(" ");
for(c='A'; c<=ch; c++)
printf("%c",c);
for(c=ch-1; c>='A'; c--)
printf("%c",c);
printf("\n");
}
getch();
return 0;
}
Edited
My C# Code:
public class Pascal_Triangle
{
public void printPascal()
{
char ch, r, c;
int sp;
Console.WriteLine("\nEnter last character of triangle : ");
ch = Convert.ToChar(Console.ReadLine());
if (ch >= 'a' && ch <= 'z')
ch = Convert.ToChar(ch - 32);
for (r = 'A'; 'A' <= ch; ch--, r++)
{
for (sp = r; sp > 'A'; sp--)
Console.WriteLine(" ");
for (c = 'A'; c <= ch; c++)
Console.Write(c);
for (c = Convert.ToChar(ch - 1); c >= 'A'; c--)
Console.Write(c);
}
Console.ReadLine();
}
}
The Output I'm getting:

C# does support looping through alphabet...
char c = 'A';
++c;
Where c would grow to 'B'
But of course, you can't increase/deacrease a string, only a character.
Your code is a way too complicated, try this. It's easy to understand, just go step by step.
Console.WriteLine("\nEnter last character of triangle : ");
char ch = Convert.ToChar(Console.ReadLine());
if (ch >= 'a' && ch <= 'z')
{
ch = Convert.ToChar(ch - 32);
}
int numberOfLines = ch - 'A' + 1;
var graphic = "";
for (var i = 0; i < numberOfLines; i++, ch--)
{
var line = "";
var tmp = "";
for (var j = 0; j < i; j++)
{
tmp += " ";
}
line += tmp;
for (var j = 'A'; j < ch; j++)
{
line += j.ToString();
}
for (var j = ch; j >= 'A'; j--)
{
line += j.ToString();
}
line += tmp;
graphic += line + "\n";
}
Console.WriteLine(graphic);
Console.ReadLine();

Create all permutations of a string incrementally c#

I am trying to create a function that will create all permutations of a string in an incremental fashion. I would like to start at:
AAAAA
...
AAAAB
...
ACCCC
...
...
ZZZZZ
I have looked around, and can't seem to find anything of that sort. I tried to create it, but it wasn't incrementally.
Any suggestions?

The "permutation" you are describing is better known as the Cartesian product. If you have an arbitrary number of sequences that you need to form the Cartesian product of, see my answer to this question on the subject:
Generating all Possible Combinations

Normally I wouldn't help these brute force type results... but seeing how many useless result you will get out of the set I figured I'd just toss this in.
var query = from c0 in Enumerable.Range(0, 26)
from c1 in Enumerable.Range(0, 26)
from c2 in Enumerable.Range(0, 26)
from c3 in Enumerable.Range(0, 26)
from c4 in Enumerable.Range(0, 26)
select new string(
new [] {
(char)('A' + c0),
(char)('A' + c1),
(char)('A' + c2),
(char)('A' + c3),
(char)('A' + c4),
}
);
BTW... if you just want the next value you can do something like this...
public static string Increment(string input)
{
var array = input.ToCharArray();
if (array.Any(c => c < 'A' || c > 'Z'))
throw new InvalidOperationException();
for (var i = array.Length-1; i >= 0; i--)
{
array[i] = (char)(array[i] + 1);
if (array[i] > 'Z')
{
array[i] = 'A';
if (i == 0)
return 'A' + new string(array);
}
else
break;
}
return new string(array);
}

A different variant where I had the idea of using modulo arithmetic. Note that I lowered the character to {A,B,C} to test it, since going up to Z for 5 letters is a lot of strings.
public IEnumerable<char[]> AlphaCombinations(int length = 5, char startChar = 'A', char endChar = 'C')
{
int numChars = endChar - startChar + 1;
var s = new String(startChar, length).ToCharArray();
for (int it = 1; it <= Math.Pow(numChars, length); ++it)
{
yield return s;
for (int ix = 0; ix < s.Length; ++ix)
if (ix == 0 || it % Math.Pow(numChars, ix) == 0)
s[s.Length - 1 - ix] = (char)(startChar + (s[s.Length - 1 - ix] - startChar + 1) % numChars);
}
}
...
foreach (var s in AlphaCombinations(5))
{
Console.WriteLine(s);
}

Bashed out quickly - I expect this could be done better:
public static IEnumerable<string> GenerateStrings(int length = 5)
{
var buffer = new char[length];
for (int i = 0; i < length; ++i)
{
buffer[i] = 'A';
}
for(;;)
{
yield return new string(buffer);
int cursor = length;
for(;;)
{
--cursor;
if (cursor < 0)
{
yield break;
}
char c = buffer[cursor];
++c;
if (c <= 'Z')
{
buffer[cursor] = c;
break;
}
else
{
buffer[cursor] = 'A';
}
}
}
}

Here is the LINQPad friendly code and it uses lambda expression.
void Main()
{
var chars = Enumerable.Range(65, 26);
var strings = chars.SelectMany (a =>
{
return chars.SelectMany (b => chars.SelectMany (c =>
{
return chars.SelectMany (d =>
{
return chars.Select (e => {return new string(new char[] {(char)a, (char)b, (char)c, (char)d, (char)e});});
});
}));
});
strings.Dump();
}