Find if two strings only differ by n characters; Return True if it does, false if it doesn't?

Question

Write a C program which accept two strings and print characters in second string which are not present in first string?

Example:
String 1: apple
String 2: aeroplane

output:
ron

Answer 1

Its simple iterative procedure see code as follows (tested one)

#include <stdio.h>
#include <string.h>    

int countdiffs(char* w1, char* w2, int diffs) {

   char *lw, *sw;
   int i, curdiffs = 0;

   if ((NULL == w1) || (NULL == w2)) {
     return 0; 
   }

   if (strlen(w2) > strlen(w1)) {
      lw = w2; 
      sw = w1; 
   } else {
     lw = w1; 
     sw = w2;
   }
   curdiffs += strlen(lw) - strlen(sw);
   if (curdiffs > diffs) {
     return 0;
   }

   for (i=0; i<strlen(sw); i++) {
     if (sw[i] != lw[i]) {
        curdiffs++;
        if (curdiffs > diffs) {
          return 0;
        }
     }
   }
   if (curdiffs == diffs) {
      return 1; 
   }
   return 0;
}


int main() {
  char *word1="QueryHome";
  char *word2="MueryHome";
  int diffs = 1; 
  int answer;

  answer = countdiffs(word1, word2, diffs);
  printf("Answer:%d\n", answer);


  answer = countdiffs("QueryHome", "MurryHome", 1);
  printf("Answer:%d\n", answer);

  return 0;
}