A Program to check if strings are rotations of each other or not | GeeksforGeeks

Given a string s1 and a string s2, write a snippet to say whether s2 is a rotation of s1 using only one call to strstr routine?

Algorithm: areRotations(str1, str2)

    1. Create a temp string and store concatenation of str1 to
       str1 in temp.
                          temp = str1.str1
    2. If str2 is a substring of temp then str1 and str2 are 
       rotations of each other.

int areRotations(char *str1, char *str2)

{

  int size1   = strlen(str1);

  int size2   = strlen(str2);

  char *temp;

  void *ptr;

  /* Check if sizes of two strings are same */

  if (size1 != size2)

     return 0;

  /* Create a temp string with value str1.str1 */

  temp   = (char *)malloc(sizeof(char)*(size1*2 + 1));

  temp[0] = '\0';

  strcat(temp, str1);

  strcat(temp, str1);

  /* Now check if str2 is a substring of temp */

  ptr = strstr(temp, str2);

  free(temp); // Free dynamically allocated memory

  /* strstr returns NULL if the second string is NOT a

    substring of first string */

  if (ptr != NULL)

    return 1;

  else

    return 0;

}

Read full article from A Program to check if strings are rotations of each other or not | GeeksforGeeks