Reverse the ordering of words in a string

Question

I have this string s1 = \"My name is X Y Z\" and I want to reverse the order of the words so that s1 = \"Z Y X is name My\".

I can do it u

Answer 1

I know there are several correct answers. Here is the one in C that I came up with. This is an implementation of the excepted answer. Time complexity is O(n) and no extra string is used.

#include

char * strRev(char *str, char tok)
{
   int len = 0, i;
   char *temp = str;
   char swap;

   while(*temp != tok && *temp != '\0') {
      len++; temp++;
   }   
   len--;

   for(i = 0; i < len/2; i++) {
      swap = str[i];
      str[i] = str[len - i]; 
      str[len - i] = swap;
   }   

   // Return pointer to the next token.
   return str + len + 1;
}

int main(void)
{
   char a[] = "Reverse this string.";
   char *temp = a;

   if (a == NULL)
      return -1; 

   // Reverse whole string character by character.
   strRev(a, '\0');

   // Reverse every word in the string again.
   while(1) {
      temp = strRev(temp, ' ');
      if (*temp == '\0')
         break;

      temp++;
   }   
   printf("Reversed string: %s\n", a); 
   return 0;
}