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

/*
 Sample midterm question:

 The C library function strstr() checks if one word is a substring of
 another. Given two strings, s1 and s2, write code to check if s2 is a
 rotation of s1 using only one call to strstr() (i.e., “waterbottle”
 is a rotation of “erbottlewat”).

 */


int main(int argc, char ** argv) {

  if (argc != 3) {
    fprintf(stderr, "Usage: strstr string1 string2\n");
    exit(1);
  }

  char * s1 = argv[1];
  char * s2 = argv[2];
  int len = strlen(s1);
  int len2 = strlen(s2);
  char * s1s1;
  if (len != len2) {
    printf("Not a rotation.\n");
  } else {
    s1s1 = (char *) malloc((len+len+1) * sizeof(s1[0]));
    strcpy(s1s1, s1);
    strcat(s1s1, s1);

    if (strstr(s1s1, s2)) {
      printf("%s is a rotation of %s\n", s1, s2);
    } else {
      printf("%s is NOT a rotation of %s\n", s1, s2);
    }
  }

  free(s1s1);
  return 0;

}