I need help for this exercise:
Inside the Test class, you must create a public method called copyText that takes a text as input and answer with a text.
It must answer with the same text put together as many time as there is characters in the input text.
Ex: in("car") out "carcarcar";
Ex: in("it") out "itit";
Ex: in("love") out "lovelovelovelove";
Ex: in("coffe") out "coffecoffecoffecoffecoffe";
I have tried to make a solution, where I find the Length of the word,
but I can't figure out to do this part:
Answer with the same text put together as many time as there are characters:
class Program
{
static void Main(string[] args)
{
Test k = new Test();
string carText = k.copyText("car");
Console.WriteLine(carText.Length);
}
}
class Test
{
public string copyText(string text)
{
return text;
}
}
You can loop through each character in the word, and append the text each time to a variable.
public string copyText(string text)
{
string output = String.Empty;
for(int i = 0; i < text.Length; i++) {
output += text;
}
return output;
}
It is good to point out that the String class is immutable and for every iteration new object will be created, which can cause high memory consumption. For concatenating strings see the StringBuilder class. I think this article will help you with your exercise.
PS: I also think you should not just copy the snippet, but really research and try to understand how it works. Then when you have more questions than answers, it will cause more and more research and actually learning.
Good luck with the coding :)
Related
Is there any way to make Search and addToSearch faster?
I am trying to make it faster. I am not sure if regex in addtosearch can be a problem, it is really small. I am out ofideas how to optimize it further. Now i am just trying to meet word count. I wonder if there is a way to concatenate parts of name that are not empty more effectivly than i do.
using System.Collections.Generic;
using System.Text.RegularExpressions;
using System;
namespace AutoComplete
{
public struct FullName
{
public string Name;
public string Surname;
public string Patronymic;
}
public class AutoCompleter
{
private List<string> listOfNames = new List<string>();
private static readonly Regex sWhitespace = new Regex(#"\s+");
public void AddToSearch(List<FullName> fullNames)
{
foreach (FullName i in fullNames)
{
string nameToAdd = "";
if (!string.IsNullOrWhiteSpace(i.Surname))
{
nameToAdd += sWhitespace.Replace(i.Surname, "") + " ";
}
if (!string.IsNullOrWhiteSpace(i.Name))
{
nameToAdd += sWhitespace.Replace(i.Name, "") + " ";
}
if (!string.IsNullOrWhiteSpace(i.Patronymic))
{
nameToAdd += sWhitespace.Replace(i.Patronymic, "") + " ";
}
listOfNames.Add(nameToAdd.Substring(0, nameToAdd.Length - 1));
}
}
public List<string> Search(string prefix)
{
if (prefix.Length > 100 || string.IsNullOrWhiteSpace(prefix))
{
throw new System.Exception();
}
List<string> namesWithPrefix = new List<string>();
foreach (string name in listOfNames)
{
if (IsPrefix(prefix, name))
{
namesWithPrefix.Add(name);
}
}
return namesWithPrefix;
}
private bool IsPrefix(string prefix, string stringToSearch)
{
if (stringToSearch.Length < prefix.Length)
{
return false;
}
for (int i = 0; i < prefix.Length; i++)
{
if (prefix[i] != stringToSearch[i])
{
return false
}
}
return true
}
}
}
Regular expression (Regexp) are great because of their ease-of use and flexibility but most Regexp engines are actually quite slow. This is the case for the one of C#. Moreover, strings can contain Unicode character and "\s" needs to consider all the (fancy) spaces characters included in the Unicode character set. This make Regexp search/replace much slower. If you know your input does not contain such characters (eg. ASCII), then you can write a much faster implementation. Alternatively, you can play with RegexpOptions like Compiled and CultureInvariant so to reduce a bit the run time.
The AddToSearch performs many hidden allocations. Indeed, += create a new string (because C# string are immutable and not designed to be often resized) and Replace calls does allocate new strings too. You can speed up the computation by directly replace and write the result in a preallocated buffer and simply copy the result with a Substring like you currently do.
Search is fine and it is not easy to optimize it. That being said, if listOfNames is big, then you can use multiple threads so to significantly speed up the computation. Be careful though because Add is not thread-safe. Parallel linkq may help you to do that easily (I never tested it though).
Another solution to speed up a bit the computation of Search is to start the loop of IsPrefix from prefix.Length-1. Indeed, if most string contains the beginning of the prefix, then a significant portion of the time will be spend comparing nearly equal characters. The probability that prefix[prefix.Length-1] != stringToSearch[prefix.Length-1] is higher than prefix[0] != stringToSearch[0]. Additionally, partial loop unrolling may help a bit to speed up the function if the JIT is not able to do that.
Others have already pointed out that the use of regex can be problematic. I would personally consider using str.Replace(" ", String.Empty) - if I understood the regex correctly; I normally try to avoid regex as I have a hard time reading code using regex. Note that String.Empty does not allocate a new string.
That said, I think performance could boost if you would not store the names in a List but at least order the list alpabetically. Thus you do not need to iterate all elemnts of the list but e.g. use binary search to find all elements matching a given prefix - as range within the list of names you already have.
I'm working on a book encryption program for one of my courses and I've run into a problem. Our professor gave us the example of using say Pride and Prejudice as the book used to encrypt, so I chose that one to test my program. The current function I'm using to remove the punctuation from the string is taking so long that the program is being forced into break mode. This function works for smaller strings even pages long, but when I fed it Pride and Prejudice it takes way to long.
public void removePunctuation(ref string s) {
string result = "";
for (int i = 0; i < s.Length; i++) {
if (Char.IsWhiteSpace(s[i])) {
result += ' ';
} else if (!Char.IsLetter(s[i]) && !Char.IsNumber(s[i])) {
// do nothing
} else {
result += s[i];
}
}
s = result;
}
So I think I need a faster way to remove punctuation from this string if anyone has any suggestions? I know looping through every character is horrible, but I'm stumped and I was never taught Regex in depth.
Edit: I was asked how I was storing the string in the dictionary class! This is the constructor for another class that actually uses the formatted string.
public CodeBook(string book)
{
BookMap = new Dictionary<string, List<int>>();
Key = book.Split(null).ToList(); // split string into words
foreach(string s in Key)
{
if (!BookMap.Keys.Contains(s))
{
BookMap.Add(s, Enumerable.Range(0, Key.Count).Where(i => Key[i] == s).ToList());
// add word and add list of occurrances of word
}
}
}
This is slow because you construct string by concatenations in a loop. You have several approaches that are more performant:
Use StringBuilder - unlike string concatenation which constructs a new object each time you add a character, this approach expands the string under construction by larger chunks, preventing excessive garbage creation.
Use LINQ's filtering with Where - this approach constructs an array of chars in a single shot, then constructs a single string from it.
Use regular expression's Replace - this method is optimized to deal with strings of virtually unlimited sizes.
Roll your own algorithm - create an array of chars that corresponds to the length of the original string. Walk through the string, and add the characters that you wish to keep to the array. Use string's constructor that takes the array, the initial index, and the length to construct the string at once.
Looping through every character once is not that bad. You're doing it all in one pass, that's not trivial to avoid.
The problem lies in the fact that the framework will need to allocate a new copy of the (partial) string whenever you do something like
result += s[i];
You can avoid that by introducing a StringBuilder documented here to append non-punctuation characters as you go.
public string removePunctuation(string s)
{
var result = new StringBuilder();
for (int i = 0; i < s.Length; i++) {
if (Char.IsWhiteSpace(s[i])) {
result.Append(" ");
} else if (!Char.IsLetter(s[i]) && !Char.IsNumber(s[i])) {
// do nothing
} else {
result.Append(s[i]);
}
}
return result.ToString();
}
You could further reduce the number of necessary Append calls with a refined algorithm, for example look ahead to the next punctuation and append larger portions at once, or use an existing string manipulation library like RegEx. But the introduction of StringBuilder above should give you a noticable performance gain already.
I was never taught Regex in depth
Use the search provider of your choice, you may end up with a tested solution which you can just study and use: https://stackoverflow.com/a/5871826/1132334
You can use Regex to remove punctuations as below.
public string removePunctuation(string s)
{
string result = Regex.Replace(s, #"[^\w\s]", "");
return result;
}
^ Means: not these characters (letters, numbers).
\w Means: word characters.
\s Means: space characters.
Im making a hangman game, at the start of the game the word that the player must guess is printed as stars. I have just started making it again after attempting to write it once and just having messy code that i couldn't bug fix. So I decided it best to write it again. The only problem is, when i try to get my array to print out by using array.ToString(); it just returns System.char[]. See below.
code:
class Program
{
static void Main(string[] args)
{
string PlayerOneWord;
string PlayerTwoGuess;
int lives = 5;
Console.WriteLine("Welcome to hangman!\n PLayer one, Please enter the word which player Two needs to guess!");
PlayerOneWord = Console.ReadLine().ToLower();
var stars = new char[PlayerOneWord.Length];
for (int i = 0; i < stars.Length ; i++)
{
stars[i] = '*';
}
string StarString = stars.ToString();
Console.Write("Word to Guess: {0}" , StarString);
Console.ReadLine();
}
}
output:
The output should say Word to guess: Hello.
Please will someone explain why this is happening as its not the first time I have run into this problem.
Calling ToString on a simple array only returns "T[]" regardless what the type T is. It doesn't have any special handling for char[].
To convert a char[] to string you can use:
string s = new string(charArray);
But for your concrete problem there is an even simpler solution:
string stars = new string('*', PlayerOneWord.Length);
The constructor public String(char c, int count) repeats c count times.
The variable stars is an array of chars. This is the reason you get this error. As it is stated in MSDN
Returns a string that represents the current object.
In order you get a string from the characters in this array, you could use this:
Console.Write("Word to Guess: {0}" , new String(stars));
The correct way to do this would be:
string StarString = new string(stars);
ToString() calls the standard implementation of the Array-class's ToString-method which is the same for all Arrays and similarily to object only returns the fully qualified class name.
Try this code:
static string ConvertCharArr2Str(char[] chs)
{
var s = "";
foreach (var c in chs)
{
s += c;
}
return s;
}
I'm working on a Hangman project that requires me to change characters "-" to "a to z". Since I'm learning how to code with C#, I have no clue how to do it.
I obviously need to use position because of the case where the word as duplicated letters (EX.: C oo kies)
Here's the code I developed, it makes my thing crashes and it's obviously incomplete.
private void chkA_Checked(object sender, RoutedEventArgs e)
{
if (motRechercher.Contains("a"))
{
int indexDemotRechercher = motRechercher.IndexOf("a");
int k = indexDemotRechercher;
var StringBuilderOP = new StringBuilder(motRechercher);
StringBuilderOP.Remove(indexDemotRechercher, indexDemotRechercher);
StringBuilderOP.Insert(k, "A");
}}
motRechercher is a STRING that I can use everywhere that I randomly pick from a list of 27 words. If this bother, it's a check-box and where I write the text is a Text-box(called txtMot).
Feel free to use other variables, I'll re-adapt after for my own comprehension. I would just like some explanation/examples to help my learning experience.
Here is the code of the randomiser if you really feel like this can help you understand[It works] :
private void btnDemarrer_Click(object sender, RoutedEventArgs e)
{
Random rdn = new Random();
int nbreAleatoire = rdn.Next(0, 27);
motRechercher = lesMots[nbreAleatoire];
if (motRechercher.Length > 0)
{
String str = new String('-', motRechercher.Length);
txtMot.Text = str;
}
}
QUESTION : How do I make a thing that detects duplicate and that will change the "-" to "a-z"?
Ask questions and I'll try to answer them if you think it's unclear.
Here is a quick sample... I have two strings... one for the hidden word the user does NOT see, and another for the one presented, using "-" or even "_" as place-holders for the actual characters.
I have a simple function "IsThereA" which expects a single letter as to the guess of a letter in the word. I then just call for all the letters including a few random ones. The function returns boolean so you can draw the hangman as each failure occurs.
In the "IsThereA" method, I am looking one character at a time for the guessed letter. If found, I replace it by using substring instead of the "-". So once updated, you can use the "WordUserCanSee" property however you need to.
This version doesn't do case-sensitive, but you can adjust as needed.
public class Hangman
{
string HangmanWord = "cookies";
string WordUserCanSee = "-------";
public Hangman()
{
IsThereA("o");
IsThereA("f");
IsThereA("k");
IsThereA("w");
IsThereA("i");
IsThereA("c");
IsThereA("s");
IsThereA("e");
}
public bool IsThereA(string guessLetter)
{
bool anyMatch = false;
for (int i = 0; i < HangmanWord.Length; i++)
{
if (HangmanWord.Substring(i, 1).Equals(guessLetter))
{
anyMatch = true;
WordUserCanSee = WordUserCanSee.Substring(0, i) + guessLetter + WordUserCanSee.Substring(i + 1);
}
}
return anyMatch;
}
}
motRechercher = motRechercher.Replace("-", "a-z");
I have a function in a class called Function, like below:
public int SearchedRecords(String [] recs)
{
int counter = 0;
String pat = "-----";
String[] records = recs;
foreach (String line in records)
{
if (line.Contains(pat) == true)
{
counter++;
}
}
return counter;
}
And I am calling this method from my main class this way:
String [] file = File.ReadAllLines("C:/Users.../results.txt");
int counter = Function.SearchedRecords( []file);
But I get an error saying:
;expected
What is wrong?
Another question: The function above is counting from a file all the lines with the pattern ----- in them (even if with more dashes, or if the line has some chars before or after the dashes). Am I right?
It's something like the patterns in Java so maybe there is an other way.
Can you enlighten me?
Remove the [] from your parameter.
e.g.
int counter = Function.SearchedRecords(file);
And yes, your assumption about the behavior of the Contains method is correct - you'll match any line containing five consecutive dashes, regardless of what characters are before or after them.
If you want to parse for exactly five dashes, with nothing before or after them I suggest looking into the RegEx class (regular expressions).
Change
int counter = Function.SearchedRecords( []file);
to
int counter = Function.SearchedRecords(file);
and yes, this will work, for that string.
However Contains is case sensitive, if you were matching on a name, or another string with alphabetic characters, the case would have to be identical to match e.g. line.Contains("Binary Worrier") will not match a string "Hello binary worrier".
Also, reading the entire file into memory is fine if you know that the file will always be small, this method gets less efficient the larger the file.
Better to always use something like System.IO.StreamReader or System.IO.File.ReadLines (available in .Net 4 and later), these allow you to consume the file one line at a time. e.g.
using (var reader = new System.IO.StreamReader("MyFile.txt"))
{
while(!reader.EndOfStream)
{
string line = reader.ReadLine();
if (line.Contains(pattern))
counter++;
}
}
Change it to
int counter = Function.SearchedRecords(file);
Remove '[]' from a method call. Yes, your function seems to count what you want.
First of all you need to create an instance of function class and then run the function. Hope following code helps
Function fb = new Function();
int counter = fb.SearchedRecords(file);
Right now, you are using SearchRecords as an static function of a static class which doesn't require instantiation.
You can do this in a shorter way using LINQ:
int counter = file.Count(line => line.Contains("-----"));