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.
C++
// C++ program to check if two given strings // are rotations of each other # include <bits/stdc++.h> using namespace std; /* Function checks if passed strings (str1 and str2) are rotations of each other */bool areRotations(string str1, string str2) { /* Check if sizes of two strings are same */ if (str1.length() != str2.length()) return false; string temp = str1 + str1; return (temp.find(str2) != string::npos); } /* Driver program to test areRotations */int main() { string str1 = "AACD", str2 = "ACDA"; if (areRotations(str1, str2)) printf("Strings are rotations of each other"); else printf("Strings are not rotations of each other"); return 0; } |
C
// C program to check if two given strings are rotations of // each other # include <stdio.h> # include <string.h> # include <stdlib.h> /* Function checks if passed strings (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] = ''; 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; } /* Driver program to test areRotations */int main() { char *str1 = "AACD"; char *str2 = "ACDA"; if (areRotations(str1, str2)) printf("Strings are rotations of each other"); else printf("Strings are not rotations of each other"); getchar(); return 0; } |
Java
// Java program to check if two given strings are rotations of // each other class StringRotation { /* Function checks if passed strings (str1 and str2) are rotations of each other */ static boolean areRotations(String str1, String str2) { // There lengths must be same and str2 must be // a substring of str1 concatenated with str1. return (str1.length() == str2.length()) && ((str1 + str1).indexOf(str2) != -1); } // Driver method public static void main (String[] args) { String str1 = "AACD"; String str2 = "ACDA"; if (areRotations(str1, str2)) System.out.println("Strings are rotations of each other"); else System.out.printf("Strings are not rotations of each other"); } } // This code is contributed by munjal |
Python
# Python program to check if strings are rotations of # each other or not # Function checks if passed strings (str1 and str2) # are rotations of each other def areRotations(string1, string2): size1 = len(string1) size2 = len(string2) temp = '' # Check if sizes of two strings are same if size1 != size2: return 0 # Create a temp string with value str1.str1 temp = string1 + string1 # Now check if str2 is a substring of temp # string.count returns the number of occurrences of # the second string in temp if (temp.count(string2)> 0): return 1 else: return 0 # Driver program to test the above function string1 = "AACD"string2 = "ACDA" if areRotations(string1, string2): print "Strings are rotations of each other"else: print "Strings are not rotations of each other" # This code is contributed by Bhavya Jain |
C#
// C# program to check if two given strings // are rotations of each other using System; class GFG { /* Function checks if passed strings (str1 and str2) are rotations of each other */ static bool areRotations(String str1, String str2) { // There lengths must be same and // str2 must be a substring of // str1 concatenated with str1. return (str1.Length == str2.Length ) && ((str1 + str1).IndexOf(str2) != -1); } // Driver method public static void Main () { String str1 = "FGABCDE"; String str2 = "ABCDEFG"; if (areRotations(str1, str2)) Console.Write("Strings are" + " rotation s of each other"); else Console.Write("Strings are " + "not rotations of each other"); } } // This code is contributed by nitin mittal. |
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
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 substrng in a string of length n where length of substring is assumed to be smaller than the string.
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