Question

Implement the following functions. Each function deals with null terminated C-strings. You can assume that any char array passed into the functions will contain valid, null-terminated data. Your functions must have the signatures listed below.

1. This function returns the last index where the target char can be found in the string. it returns -1 if the target char does not appear in the string. For example, if s is “Giants” and target is ‘a’ the function returns 2.

int lastIndexOf(char *s, char target)

2. This function alters any string that is passed in. It should reverse the string. If “flower” gets passed in it should be reversed in place to “rewolf”. To be clear, just printing out the string in reverse order is insufficient to receive credit, you must change the actual string to be in reverse order.

void reverse(char *s)

3. This function finds all instances of the char ‘target’ in the string and replaces them with ‘replacementChar’. It also returns the number of replacements that it makes. If the target char does not appear in the string it returns 0 and does not change the string. For example, if s is “go giants”, target is ‘g’, and replacement is ‘G’, the function should change s to “Go Giants” and return 2.

int replace(char *s, char target, char replacementChar)

4. This function returns the index in string s where the substring can first be found. For example if s is “Skyscraper” and substring is “ysc” the function would return 2. It should return -1 if the substring does not appear in the string.

int findSubstring(char *s, char substring[])

5. This function returns true if the argument string is a palindrome. It returns false if it is not. A palindrome is a string that is spelled the same as its reverse. For example “abba” is a palindrome. So is “hannah”, “abc cba”, and “radar”.

bool isPalindrome(char *s)

Note: do not get confused by white space characters. They should not get any special treatment. “abc ba” is not a palindrome. It is not identical to its reverse.

Answer 1

int lastIndexOf(char *s, char target)
{
        int length = 0, i = 0, index;

        while(s[i] != '\0')
        {
                length++;
                i++;
        }

        index = -1;
        for(i = length - 1; i >= 0; i--)
        {
                if(s[i] == target)
                {
                        index = i;
                        break;
                }
        }

        return index;
}

void reverse(char *s)
{
        int length = 0, i = 0, j;
        char tmp[100];

        while(s[i] != '\0')
        {
                length++;
                i++;
        }

        i = length - 1;
        j = 0;
        while(i >= 0)
        {
                tmp[j] = s[i];
                i--;
                j++;
        }

        tmp[j] = '\0';
        s = tmp;
}

int replace(char *s, char target, char replacementChar)
{
        int count,i;
        count = 0;
        i = 0;

        while(s[i] != '\0')
        {
                if(s[i] == target)
                {
                        s[i] = replacementChar;
                        count++;
                }
        }

        return count;
}

int findSubstring(char *s, char substring[])
{
        int stringLength = 0, substringLength = 0, i, j;

        i = 0;
        while(s[i] != '\0')
        {
                stringLength++;
                i++;
        }

        i = 0;
        while(substring[i] != '\0')
        {
                substringLength++;
                i++;
        }
  
    
    for (i = 0; i <= stringLength - substringLength; i++) 
    { 
                for (j = 0; j < substringLength; j++) 
                {
            if (s[i + j] != substring[j]) 
                break; 
                }
  
        if (j == substringLength) 
        {
            return i; 
        }
    } 
  
    return -1; 
}

bool isPalindrome(char *s)
{
        bool value = true;
        int length = 0, i = 0, j, index;

        while(s[i] != '\0')
        {
                length++;
                i++;
        }

        for(i = 0, j = length - 1; i < length, j >= 0; i++, j--)
        {
                if(s[i] != s[j])
                {
                        value = false;
                        break;
                }
        }

        return value;
}

ALL THE FUNCTIONS ARE GIVEN IN ABOVE CODE.

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