Left Rotation and Right Rotation of a String
Given a string of size n, write functions to perform the following operations on a string-
- Left (Or anticlockwise) rotate the given string by d elements (where d <= n)
- Right (Or clockwise) rotate the given string by d elements (where d <= n).
Examples:
Input : s = "GeeksforGeeks" d = 2 Output : Left Rotation : "eksforGeeksGe" Right Rotation : "ksGeeksforGee" Input : s = "qwertyu" d = 2 Output : Left rotation : "ertyuqw" Right rotation : "yuqwert"
Method#1: A Simple Solution is to use a temporary string to do rotations. For left rotation, first, copy last n-d characters, then copy first d characters in order to the temporary string. For right rotation, first, copy last d characters, then copy n-d characters.
Can we do both rotations in-place and O(n) time?
The idea is based on a reversal algorithm for rotation.
// Left rotate string s by d (Assuming d <= n) leftRotate(s, d) reverse(s, 0, d-1); // Reverse substring s[0..d-1] reverse(s, d, n-1); // Reverse substring s[d..n-1] reverse(s, 0, n-1); // Reverse whole string. // Right rotate string s by d (Assuming d <= n) rightRotate(s, d) // We can also call above reverse steps // with d = n-d. leftRotate(s, n-d)
Below is the implementation of the above steps :
C++
// C program for Left Rotation and Right // Rotation of a String #include<bits/stdc++.h> using namespace std; // In-place rotates s towards left by d void leftrotate(string &s, int d) { reverse(s.begin(), s.begin()+d); reverse(s.begin()+d, s.end()); reverse(s.begin(), s.end()); } // In-place rotates s towards right by d void rightrotate(string &s, int d) { leftrotate(s, s.length()-d); } // Driver code int main() { string str1 = "GeeksforGeeks" ; leftrotate(str1, 2); cout << str1 << endl; string str2 = "GeeksforGeeks" ; rightrotate(str2, 2); cout << str2 << endl; return 0; } |
Java
// Java program for Left Rotation and Right // Rotation of a String import java.util.*; import java.io.*; class GFG { // function that rotates s towards left by d static String leftrotate(String str, int d) { String ans = str.substring(d) + str.substring( 0 , d); return ans; } // function that rotates s towards right by d static String rightrotate(String str, int d) { return leftrotate(str, str.length() - d); } // Driver code public static void main(String args[]) { String str1 = "GeeksforGeeks" ; System.out.println(leftrotate(str1, 2 )); String str2 = "GeeksforGeeks" ; System.out.println(rightrotate(str2, 2 )); } } // This code is contributed by rachana soma |
Python3
# Python3 program for Left # Rotation and Right # Rotation of a String # In-place rotates s towards left by d def leftrotate(s, d): tmp = s[d : ] + s[ 0 : d] return tmp # In-place rotates s # towards right by d def rightrotate(s, d): return leftrotate(s, len (s) - d) # Driver code if __name__ = = "__main__" : str1 = "GeeksforGeeks" print (leftrotate(str1, 2 )) str2 = "GeeksforGeeks" print (rightrotate(str2, 2 )) # This code is contributed by Rutvik_56 |
C#
// C# program for Left Rotation and Right // Rotation of a String using System; class GFG { // function that rotates s towards left by d static String leftrotate(String str, int d) { String ans = str.Substring(d,str.Length-d) + str.Substring(0, d); return ans; } // function that rotates s towards right by d static String rightrotate(String str, int d) { return leftrotate(str, str.Length - d); } // Driver code public static void Main(String []args) { String str1 = "GeeksforGeeks" ; Console.WriteLine(leftrotate(str1, 2)); String str2 = "GeeksforGeeks" ; Console.WriteLine(rightrotate(str2, 2)); } } /* This code is contributed by PrinciRaj1992 */ |
Javascript
<script> // JavaScript program for Left Rotation and Right // Rotation of a String // Function that rotates s towards left by d function leftrotate(str, d) { var ans = str.substring(d, str.length) + str.substring(0, d); return ans; } // Function that rotates s towards right by d function rightrotate(str, d) { return leftrotate(str, str.length - d); } // Driver code var str1 = "GeeksforGeeks" ; document.write(leftrotate(str1, 2) + "<br>" ); var str2 = "GeeksforGeeks" ; document.write(rightrotate(str2, 2) + "<br>" ); // This code is contributed by rdtank </script> |
eksforGeeksGe ksGeeksforGee
Time Complexity: O(N), where N is the size of the given string.
Auxiliary Space: O(1), no extra space is required, so it is a constant.
Method#2: We can use extended string which is double in size of normal string to rotate string. For left rotation, access the extended string from index n to the index len(string) + n. For right rotation, rotate the string left with size-d places.
The idea is
// Left rotate string s by d leftRotate(s, n) temp = s + s; // extended string l1 = s.length // length of string return temp[n : l1+n] //return rotated string. // Right rotate string s by n rightRotate(s, n) // We can also call above reverse steps // with x = s.length - n. leftRotate(s, x-n)
Below is implementation of above approach
C++
// C++ program for Left Rotation and Right // Rotation of a String #include <bits/stdc++.h> using namespace std; // Rotating the string using extended string string leftrotate(string str1, int n) { // creating extended string and index for new rotated // string string temp = str1 + str1; int l1 = str1.size(); string Lfirst = temp.substr(n, l1); // now returning string return Lfirst; } // Rotating the string using extended string string rightrotate(string str1, int n) { return leftrotate(str1, str1.size() - n); } // Driver code int main() { string str1 = leftrotate( "GeeksforGeeks" , 2); cout << str1 << endl; string str2 = rightrotate( "GeeksforGeeks" , 2); cout << str2 << endl; return 0; } |
Java
// Java program for Left Rotation and Right // Rotation of a String import java.io.*; import java.util.*; class GFG { // Rotating the string using extended string static String leftrotate(String str1, int n) { // creating extended string and index for new // rotated string String temp = str1 + str1; int l1 = str1.length(); String Lfirst = temp.substring(n, n + l1); // now returning string return Lfirst; } // Rotating the string using extended string static String rightrotate(String str1, int n) { return leftrotate(str1, str1.length() - n); } // Driver code public static void main(String args[]) { String str1 = "GeeksforGeeks" ; System.out.println(leftrotate(str1, 2 )); String str2 = "GeeksforGeeks" ; System.out.println(rightrotate(str2, 2 )); } } // This code is contributed by Abhijeet Kumar(abhijeet19403) |
Python3
# Python3 program for Left # Rotation and Right # Rotation of a String def leftrotate(str1, n): # extended string temp = str1 + str1 l = len (str1) # Return string return temp[n :l + n] def rightrotate(str1, n): return leftrotate(str1, len (str1) - n) return temp[l - n : l1 - n ] # Driver code if __name__ = = "__main__" : str1 = "GeeksforGeeks" print (leftrotate(str1, 2 )) str2 = "GeeksforGeeks" print (rightrotate(str2, 2 )) # This code is contributed by sam snehil |
C#
// C# program for Left Rotation and Right // Rotation of a String using System; class GFG { // Rotating the string using extended string static String leftrotate(String str1, int n) { // creating extended string and index for new // rotated string String temp = str1 + str1; int l1 = str1.Length; String Lfirst = temp.Substring(n, l1); // now returning string return Lfirst; } // Rotating the string using extended string static String rightrotate(String str1, int n) { return leftrotate(str1, str1.Length - n); } // Driver code public static void Main(String[] args) { String str1 = "GeeksforGeeks" ; Console.WriteLine(leftrotate(str1, 2)); String str2 = "GeeksforGeeks" ; Console.WriteLine(rightrotate(str2, 2)); } } // This code is contributed by Abhijeet Kumar(abhijeet19403) |
Javascript
// JavaScript program for Left Rotation and Right // Rotation of a String // Function that rotates string towards left by n function leftrotate(str1, n) { var temp = str1 + str1; var l1 = str1.length; var Lfirst = temp.substr(n,l1); // now returning string return Lfirst; } // Function that rotates string towards right by n function rightrotate(str, d) { return leftrotate(str, str.length - d); } // Driver code var str1 = "GeeksforGeeks" ; console.log(leftrotate(str1, 2)); var str2 = "GeeksforGeeks" ; console.log(rightrotate(str2, 2) ); // This code is contributed by sam snehil |
eksforGeeksGe ksGeeksforGee
Time Complexity: O(N), where N is the size of the given string.
Auxiliary Space: O(n), where N is the size of the given string.
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