Failing testcase for input string = " ". Replacing string in place in C.

  • 0
    • Reverse the string and then reverse each word. To accomplish this i have a function 'reverseStrings' which simply reverses strings in place. From the main function I invoke this function for the entire string and then each word.
    • My code fails the testcase where input = " ". Obviously, the expected output should also be " ". But the testcase expects "" to be returned.
    • if anyone else has faced this problem, please let me know. Also did you handle this case explicitly ?
    void reverseStrings(char *s,  int length) {
        int i;
        for(i=0; i<length/2; i++){
            char ch = s[i];
            s[i] = s[length-1-i];
            s[length-1-i] = ch;
    void reverseWords(char *s) {
        if(s == NULL || strcmp(s, " ") == 0){
        int len =  strlen(s);
        reverseStrings(s, len);
        int j;
        int start_index = 0;
        for(j = 0; j<len; j++){
            if(s[j] == ' '){
                reverseStrings(s+start_index, j-start_index);
                start_index = j+1;
        reverseStrings(s+start_index, j-start_index);

  • 0

    The expected output is correct. As the clarification says:

    Could the input string contain leading or trailing spaces?
    Yes. However, your reversed string should not contain leading or trailing spaces.

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