Develop Reference

Adding 'space' in C# textbox

Hi guys, so I need to add a 'space' between each character in my displayed text box.
I am giving the user a masked word like this He__o for him to guess and I want to convert this to H e _ _ o
I am using the following code to randomly replace characters with '_'
char[] partialWord = word.ToCharArray();
int numberOfCharsToHide = word.Length / 2; //divide word length by 2 to get chars to hide
Random randomNumberGenerator = new Random(); //generate rand number
HashSet<int> maskedIndices = new HashSet<int>(); //This is to make sure that I select unique indices to hide. Hashset helps in achieving this
for (int i = 0; i < numberOfCharsToHide; i++) //counter until it reaches words to hide
{
int rIndex = randomNumberGenerator.Next(0, word.Length); //init rindex
while (!maskedIndices.Add(rIndex))
{
rIndex = randomNumberGenerator.Next(0, word.Length); //This is to make sure that I select unique indices to hide. Hashset helps in achieving this
}
partialWord[rIndex] = '_'; //replace with _
}
return new string(partialWord);
I have tried : partialWord[rIndex] = '_ ';however this brings the error "Too many characters in literal"
I have tried : partialWord[rIndex] = "_ "; however this returns the error " Cannot convert type string to char.
Any idea how I can proceed to achieve a space between each character?
Thanks

The following code should do as you ask. I think the code is pretty self explanatory., but feel free to ask if anything is unclear as to the why or how of the code.
// char[] partialWord is used from question code
char[] result = new char[(partialWord.Length * 2) - 1];
for(int i = 0; i < result.Length; i++)
{
result[i] = i % 2 == 0 ? partialWord[i / 2] : ' ';
}
return new string(result);

Since the resulting string is longer than the original string, you can't use only one char array because its length is constant.
Here's a solution with StringBuilder:
var builder = new StringBuilder(word);
for (int i = 0 ; i < word.Length ; i++) {
builder.Insert(i * 2, " ");
}
return builder.ToString().TrimStart(' '); // TrimStart is called here to remove the leading whitespace. If you want to keep it, delete the call.

C# Test Box Manipulation when reading from a File

I am trying to code a simple game where my program randomly selects a word from a dictionary and stores it in a text box/or label? (Not Sure of this part). Then I have another text box where the user enters his guess.
Now I want to give the user some hint.F or example the word:
'game' would look like '_ a m _' or 'g _ _ e'. I have no preference to how the characters are placed.
I have programmed all of the previous code including the random file handling method, all timers and counter etc. I am just stuck on this part.
The program undergoes the following code :
var lines = File.ReadAllLines(#"LOCATION");
textBox3.Text = lines[new Random().Next(lines.Length)];
to select a random word from the file. However the whole word is being shown in textbox 3 and not parts of it like i wish. I am at a complete loss for ideas on how to proceed. I could not find anything similar on the web.
Cheers,
R

Once you pick a random word from file, based on length of the word, decide on how many characters you'd want to hide and then randomly replace those many characters.
something like this-
public string GetPartialWord(string word)
{
if(string.IsNullOrEmpty(word))
{
return string.Empty;
}
char[] partialWord = word.ToCharArray();
int numberOfCharsToHide = word.Length / 2;
Random randomNumberGenerator = new Random();
HashSet<int> maskedIndices = new HashSet<int>();
for(int i=0;i<numberOfCharsToHide;i++)
{
int rIndex = randomNumberGenerator.Next(0, word.Length);
while(!maskedIndices.Add(rIndex))
{
rIndex = randomNumberGenerator.Next(0, word.Length);
}
partialWord[rIndex] = '_';
}
return new string(partialWord);
}

The code below will replace at least half of the characters with underscores. The code takes a word and keeps generating random numbers until it has replaced at least half of the characters with underscores.
public string ConvertToGuessWord(string word)
{
var guessWord = word;
int lastRandom = 0;
do
{
Random rand = new Random();
int thisRandom = 0;
do
{
thisRandom = rand.Next(0, guessWord.Length);
} while (lastRandom == thisRandom);
guessWord = guessWord.Replace(guessWord[thisRandom], '_');
lastRandom = thisRandom;
} while (guessWord.Count(x => x == '_') < (word.Length / 2));
return guessWord;
}

erroneous character fixing of strings in c#

I have five strings like below,
ABBCCD
ABBDCD
ABBDCD
ABBECD
ABBDCD
all the strings are basically same except for the fourth characters. But only the character that appears maximum time will take the place. For example here D was placed 3 times in the fourth position. So, the final string will be ABBDCD. I wrote following code, but it seemed to be less efficient in terms of time. Because this function can be called million times. What should I do to improve the performance?
Here changedString is the string to be matched with other 5 strings. If Any position of the changed string is not matched with other four, then the maxmum occured character will be placed on changedString.
len is the length of the strings which is same for all strings.
for (int i = 0; i < len;i++ )
{
String findDuplicate = string.Empty + changedString[i] + overlapStr[0][i] + overlapStr[1][i] + overlapStr[2][i] +
overlapStr[3][i] + overlapStr[4][i];
char c = findDuplicate.GroupBy(x => x).OrderByDescending(x => x.Count()).First().Key;
if(c!=changedString[i])
{
if (i > 0)
{
changedString = changedString.Substring(0, i) + c +
changedString.Substring(i + 1, changedString.Length - i - 1);
}
else
{
changedString = c + changedString.Substring(i + 1, changedString.Length - 1);
}
}
//string cleanString = new string(findDuplicate.ToCharArray().Distinct().ToArray());
}

I'm not quite sure what you are going to do, but if it is about sorting strings by some n-th character, then the best way is to use Counting Sort http://en.wikipedia.org/wiki/Counting_sort It is used for sorting array of small integers and is quite fine for chars. It has linear O(n) time. The main idea is that if you know all your possible elements (looks like they can be only A-Z here) then you can create an additional array and count them. For your example it will be {0, 0, 1 ,3 , 1, 0,...} if we use 0 for 'A', 1 for 'B' and so on.

There is a function that might help performance-wise as it runs five times faster. The idea is to count occurrences yourself using a dictionary to convert character to a position into counting array, increment value at this position and check if it is greater than previously highest number of occurrences. If it is, current character is top and is stored as result. This repeats for each string in overlapStr and for each position within the strings. Please read comments inside code to see details.
string HighestOccurrenceByPosition(string[] overlapStr)
{
int len = overlapStr[0].Length;
// Dictionary transforms character to offset into counting array
Dictionary<char, int> char2offset = new Dictionary<char, int>();
// Counting array. Each character has an entry here
int[] counters = new int[overlapStr.Length];
// Highest occurrence characters found so far
char[] topChars = new char[len];
for (int i = 0; i < len; ++i)
{
char2offset.Clear();
// faster! char2offset = new Dictionary<char, int>();
// Highest number of occurrences at the moment
int highestCount = 0;
// Allocation of counters - as previously unseen character arrives
// it is given a slot at this offset
int lastOffset = 0;
// Current offset into "counters"
int offset = 0;
// Small optimization. As your data seems very similar, this helps
// to reduce number of expensive calls to TryGetValue
// You might need to remove this optimization if you don't have
// unused value of char in your dataset
char lastChar = (char)0;
for (int j = 0; j < overlapStr.Length; ++ j)
{
char thisChar = overlapStr[j][i];
// If this is the same character as last one
// Offset already points to correct cell in "counters"
if (lastChar != thisChar)
{
// Get offset
if (!char2offset.TryGetValue(thisChar, out offset))
{
// First time seen - allocate & initialize cell
offset = lastOffset;
counters[offset] = 0;
// Map character to this cell
char2offset[thisChar] = lastOffset++;
}
// This is now last character
lastChar = thisChar;
}
// increment and get count for character
int charCount = ++counters[offset];
// This is now highestCount.
// TopChars receives current character
if (charCount > highestCount)
{
highestCount = charCount;
topChars[i] = thisChar;
}
}
}
return new string(topChars);
}
P.S. This is certainly not the best solution. But as it is significantly faster than original I thought I should help out.

Breaking Down & Rearranging String into all possible combinations

I want to break down and rearranging a string into all possible combinations
Say I have a String: ABCDEF
I want to break it down and output all possible combinations
Combination(6,6) = 1
ABCDEF
Combination(6,5) = 6
BCDEF
ACDEF
ABDEF
ABCEF
ABCDF
ABCDE
Combination(6,4) = 15
BCDE
ACDE
ABDE
ABCE
....
....
....
etc.
Combination(6,3) = 20
BCD
ACD
...
etc.
Combination(6,2) = 15
BC
AB
etc.
However the ouptut must also be arranged into alphabetical order.
How will I do this?
Thanks! Any help will be appreciated!

You can get the algorithm (actually a few of them) from Knuth Volume 4, Fascicle 3 but you'll have to convert it from his math notation to C#.
Update: As I think about this more, Fascicle 2 (Generating Permutations) is actually more helpful. You can download it free from http://www-cs-faculty.stanford.edu/~knuth/fasc2b.ps.gz though you'll need gunzip and a PostScript previewer to read it. Generating the subsets of string "ABCDE" is the easy part. Convert it to an array {'A', 'B', 'C', 'D', 'E'}, run a for loop from 0 to 2^N-1 where N is the array length, and treat each value as a bitmask of the elements you're keeping. Thus 00001, 00010, 00011,... gives you "A", "B", "AB",...
The hard part is generating all the permutations of each subset, so you get "ABC", "BAC", "CAB", etc. A brute force algorithm (like in one of the other answers) will work but will get very slow if the string is long. Knuth has some fast algorithms, some of which will generate the permutations in alphabetical order if the original string was sorted in the first place.

Well, to expand on my comment, how I got past this problem was transforming the string into a hash that doesn't care the order of the letters. The hash works by taking each unique letter, then a :, then the number of times that letter occurs.
So test = e:1,s:1,t:2
Then if somebody looks for the world tset, it would generate the same hash (e:1,s:1,t:2), and bam you have a match.
I just ran a word list (of about 20 million words), generated a hash for each one of them, and put it in a mysql table, I can find all permutations of a word (that are still words themselves, aka ered will return deer and reed) in seconds.

You can generate each permutation by incrementing a counter and converting the counter value to base n where n is the number of letters in your input. Discard any values containing repeating letters and what you have left are the possible scrabble words in alphabetic order assuming your array was sorted.
You will have to count up to (n^(n-1))*(n+1) to get the e*n! possible scrabble words.
char[] Letters = new char[] { 'A', 'B', 'C', 'D', 'E', 'F' };
// calculate e*n! (int)Math.Floor(Math.E * Math.Factorial(Letters.Length))
int x = 0;
for (int i = 1; i <= Letters.Length; i++)
x = (x + 1) * i;
for (int i = 1; x > 0; i++)
{
string Word = BaseX(i, Letters.Length, Letters);
if (NoRepeat(Word))
{
Console.WriteLine(Word);
x--;
}
}
BaseX returns the string representation of Value for the given Base and specified Symbols:
string BaseX(int Value, int Base, char[] Symbols)
{
StringBuilder s = new StringBuilder();
while (Value > Base)
{
s.Insert(0, Symbols[Value % Base]);
Value /= Base;
}
s.Insert(0, Symbols[Value - 1]);
return s.ToString();
}
NoRepeat returns false if any letter occurs more than once:
bool NoRepeat(string s)
{
bool[] Test = new bool[256];
foreach (char c in s)
if (Test[(byte)c])
return false;
else
Test[(byte)c] = true;
return true;
}

Sort the string in alphabet order. Say ABCDEF (your example)
Prepare a map between index and character
map[0] = 'A'; map[1] = 'B'; ... map[5] = 'F'
3 . Now your job is a lot more simple: find all combinations of number in which the later number is larger than the former
Combination(6,3):
for (int i = 0; i < 6 - 2; i++)
for (int j = i + 1; j < 6 - 1; j++)
for (int k = j + 1; k < 6; k++)
{
string strComb = map[i] + map[j] + map[k];
}
This is mainly the idea, you could improve in your own way.
Contact me if you want more detail!

You can use this:
static List<string> list = new List<string>();
static string letters = "bcdehijkmnopqrstuvwxyz";
static void Combine(string combinatory)
{
if(combinatory.Length < letters.Length)
{
Parallel.ForEach(letters, l =>
{
if (!combinatory.Contains(l)) Combine(combinatory + l);
});
} else
{
list.Add(combinatory);
Console.WriteLine(combinatory);
}
}
It will add to the list List all the possible combinations.
Then you can use the Sort() method in order to sort the list.

What is the most efficient way to detect if a string contains a number of consecutive duplicate characters in C#?

For example, a user entered "I love this post!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
the consecutive duplicate exclamation mark "!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!" should be detected.

The following regular expression would detect repeating chars. You could up the number or limit this to specific characters to make it more robust.
int threshold = 3;
string stringToMatch = "thisstringrepeatsss";
string pattern = "(\\d)\\" + threshold + " + ";
Regex r = new Regex(pattern);
Match m = r.Match(stringToMatch);
while(m.Success)
{
Console.WriteLine("character passes threshold " + m.ToString());
m = m.NextMatch();
}

Here's and example of a function that searches for a sequence of consecutive chars of a specified length and also ignores white space characters:
public static bool HasConsecutiveChars(string source, int sequenceLength)
{
if (string.IsNullOrEmpty(source))
return false;
if (source.Length == 1)
return false;
int charCount = 1;
for (int i = 0; i < source.Length - 1; i++)
{
char c = source[i];
if (Char.IsWhiteSpace(c))
continue;
if (c == source[i+1])
{
charCount++;
if (charCount >= sequenceLength)
return true;
}
else
charCount = 1;
}
return false;
}
Edit fixed range bug :/

Can be done in O(n) easily: for each character, if the previous character is the same as the current, increment a temporary count. If it's different, reset your temporary count. At each step, update your global if needed.
For abbccc you get:
a => temp = 1, global = 1
b => temp = 1, global = 1
b => temp = 2, global = 2
c => temp = 1, global = 2
c => temp = 2, global = 2
c => temp = 3, global = 3
=> c appears three times. Extend it to get the position, then you should be able to print the "ccc" substring.
You can extend this to give you the starting position fairly easily, I'll leave that to you.

Here is a quick solution I crafted with some extra duplicates thrown in for good measure. As others pointed out in the comments, some duplicates are going to be completely legitimate, so you may want to narrow your criteria to punctuation instead of mere characters.
string input = "I loove this post!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!aa";
int index = -1;
int count =1;
List<string> dupes = new List<string>();
for (int i = 0; i < input.Length-1; i++)
{
if (input[i] == input[i + 1])
{
if (index == -1)
index = i;
count++;
}
else if (index > -1)
{
dupes.Add(input.Substring(index, count));
index = -1;
count = 1;
}
}
if (index > -1)
{
dupes.Add(input.Substring(index, count));
}

The better way i my opinion is create a array, each element in array is responsible for one character pair on string next to each other, eg first aa, bb, cc, dd. This array construct with 0 on each element.
Solve of this problem is a for on this string and update array values.
You can next analyze this array for what you want.
Example: For string: bbaaaccccdab, your result array would be { 2, 1, 3 }, because 'aa' can find 2 times, 'bb' can find one time (at start of string), 'cc' can find three times.
Why 'cc' three times? Because 'cc'cc & c'cc'c & cc'cc'.

Use LINQ! (For everything, not just this)
string test = "aabb";
return test.Where((item, index) => index > 0 && item.Equals(test.ElementAt(index)));
// returns "abb", where each of these items has the previous letter before it
OR
string test = "aabb";
return test.Where((item, index) => index > 0 && item.Equals(test.ElementAt(index))).Any();
// returns true