Php Program to check if strings are rotations of each other or not
Given a string s1 and a string s2, write a snippet to say whether s2 is a rotation of s1? (eg given s1 = ABCD and s2 = CDAB, return true, given s1 = ABCD, and s2 = ACBD , return false) 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. Example: str1 = "ABACD" str2 = "CDABA" temp = str1.str1 = "ABACDABACD" Since str2 is a substring of temp, str1 and str2 are rotations of each other.
PHP
<?php // Php program to check if // two given strings are // rotations of each other /* Function checks if passed strings (str1 and str2) are rotations of each other */ function areRotations( $str1 , $str2 ) { /* Check if sizes of two strings are same */ if ( strlen ( $str1 ) != strlen ( $str2 )) { return false; } $temp = $str1 + $str1 ; if ( $temp . count ( $str2 )> 0) { return true; } else { return false; } } // Driver code $str1 = "AACD" ; $str2 = "ACDA" ; if (areRotations( $str1 , $str2 )) { echo "Strings are rotations " . "of each other" ; } else { echo "Strings are not " . "rotations of each other" ; } // This code is contributed // by Shivi_Aggarwal. ?> |
Output:
Strings are rotations of each other
Time Complexity: O(n*n), where n is the length of the string.
Auxiliary Space: O(n)
Library Functions Used: strstr: strstr finds a sub-string within a string. Prototype: char * strstr(const char *s1, const char *s2); See http://www.lix.polytechnique.fr/Labo/Leo.Liberti/public/computing/prog/c/C/MAN/strstr.htm for more details strcat: strncat concatenate two strings Prototype: char *strcat(char *dest, const char *src); See http://www.lix.polytechnique.fr/Labo/Leo.Liberti/public/computing/prog/c/C/MAN/strcat.htm for more details Time Complexity: Time complexity of this problem depends on the implementation of strstr function. If implementation of strstr is done using KMP matcher then complexity of the above program is (-)(n1 + n2) where n1 and n2 are lengths of strings. KMP matcher takes (-)(n) time to find a substring in a string of length n where length of substring is assumed to be smaller than the string. Please refer complete article on A Program to check if strings are rotations of each other or not for more details!
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