CODEWITHSUNDEEP
c#arrays
The Muffin Man
The Muffin Man

Reputation: 20004

Trim a char array

Background: I was invited to an interview at a high profile company and I was asked the following question before being told I failed the interview for the position (C#,mvc3,razor). I'm genuinely interested in how to solve this.

Question: "Write a method that takes a char array, trims whitespace, and returns the same array." After some thinking I was told to replace the whitespace with "\o".

I started with:

public static char[] Trim(char[] c)
    {
        for (int i = 0; i < c.Length; i++)
        {
            if (c[i] == '\r' || c[i] == '\n' || c[i] == '\t')
            {
                c[i] = '\o';
            }     
        }
    }

I was told I have to use the same array, can't put it in a list and call ToArray(). However I think if the array stays the same size it is impossible to "trim it".

Upvotes: 5

Views: 9497

Answers (5)

Dai
Dai

Reputation: 155145

Assuming they meant to replace whitespace characters with null characters then the solution is simple:

Step 1: From the start of the string (represented as a character array) replace whitespace characters until a non-WS character is encountered.

Step 2: From the end of the string, working backwards, do the same.

public static void Trim( Char[] chars )
{        
    int maxIdx = 0; // an optimization so it doesn't iterate through chars already encountered
    for( int i = 0;i < chars.Length; i++ )
    {
        if( Char.IsWhitespace( chars[i] ) )
        {
            chars[i] = '\0';
        }
        else
        {
            maxIdx = i;
            break;
        }
    }

    for( int i = chars.Length - 1; i > maxIdx; i-- )
    {
        if( Char.IsWhitespace( chars[i] ) ) chars[i] = '\0';
    }
}

Upvotes: 3

Gaurav
Gaurav

Reputation: 1

I guess what you might have been asked is to remove white space from between the string and then fill the char array for the remaining elements of the array with '\0'

e.g. "Convert this string" to "Convertthisstring" and fill the remaining array with 2 '\0'

Solution:

    char[] TrimWhiteSpace(char[] source)
    {
        int i, j = 0;

        for (i = 0; i < source.Length; i++)
        {
            if (!char.IsWhiteSpace(source[i]))
            {
                source[j] = source[i];
                j++;
            }
        }

        for (int x = 0; x < (i - j); x++)
        {
            source[j + x] = '\0';
        }

        return source;
    }

Upvotes: 0

Larsenal
Larsenal

Reputation: 51156

This is ugly and untested, but it does the whole thing in a single pass without creating a new array:

public static void Trim(Char[] str) {

    int nonNullIndex = 0;
    int lastNonNullIndex = 0;

    for(int i=0;i<str.Length;i++) {
        str[nonNullIndex] = str[i];
        if( !Char.IsWhitespace( str[i] ) || nonNullIndex > 0) nonNullIndex++;
        if( !Char.IsWhitespace( str[i] )) lastNonNullIndex = i;
    }
    nonNullIndex++
    str[lastNonNullIndex] = '\0';

}

Upvotes: 0

BlackSpy
BlackSpy

Reputation: 5603

public static char[] Trim(char[] str)
{
  return str.Where(x => !Char.IsWhiteSpace(x)).ToArray();
}

Upvotes: 2

Karthik Kumar Viswanathan
Karthik Kumar Viswanathan

Reputation: 1806

They may have meant \0 (NUL character), not dash-0

Upvotes: 6

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