Write code to find lexicographic minimum in a circular array, e.g. for the array BCABDADAB, the lexicographic minimum is ABBCABDAD.
Source: Google Written Test
More Examples:
Input: GEEKSQUIZ Output: EEKSQUIZG Input: GFG Output: FGG Input: GEEKSFORGEEKS Output: EEKSFORGEEKSG
Following is a simple solution. Let the given string be ‘str’
1) Concatenate ‘str’ with itself and store in a temporary string say ‘concat’.
2) Create an array of strings to store all rotations of ‘str’. Let the array be ‘arr’.
3) Find all rotations of ‘str’ by taking substrings of ‘concat’ at index 0, 1, 2..n-1. Store these rotations in arr[]
4) Sort arr[] and return arr[0].
Following is the implementation of above solution.
C++
// A simple C++ program to find lexicographically minimum rotation// of a given string#include <iostream>#include <algorithm>using namespace std; // This functionr return lexicographically minimum// rotation of strstring minLexRotation(string str){ // Find length of given string int n = str.length(); // Create an array of strings to store all rotations string arr[n]; // Create a concatenation of string with itself string concat = str + str; // One by one store all rotations of str in array. // A rotation is obtained by getting a substring of concat for (int i = 0; i < n; i++) arr[i] = concat.substr(i, n); // Sort all rotations sort(arr, arr+n); // Return the first rotation from the sorted array return arr[0];} // Driver program to test above functionint main(){ cout << minLexRotation("GEEKSFORGEEKS") << endl; cout << minLexRotation("GEEKSQUIZ") << endl; cout << minLexRotation("BCABDADAB") << endl;} |
Java
// A simple Java program to find // lexicographically minimum rotation// of a given Stringimport java.util.*; class GFG{ // This functionr return lexicographically // minimum rotation of str static String minLexRotation(String str) { // Find length of given String int n = str.length(); // Create an array of strings // to store all rotations String arr[] = new String[n]; // Create a concatenation of // String with itself String concat = str + str; // One by one store all rotations // of str in array. A rotation is // obtained by getting a substring of concat for (int i = 0; i < n; i++) { arr[i] = concat.substring(i, i + n); } // Sort all rotations Arrays.sort(arr); // Return the first rotation // from the sorted array return arr[0]; } // Driver code public static void main(String[] args) { System.out.println(minLexRotation("GEEKSFORGEEKS")); System.out.println(minLexRotation("GEEKSQUIZ")); System.out.println(minLexRotation("BCABDADAB")); }} // This code is contributed by 29AjayKumar |
Python3
# A simple Python3 program to find lexicographically # minimum rotation of a given string # This function return lexicographically minimum# rotation of strdef minLexRotation(str_) : # Find length of given string n = len(str_) # Create an array of strings to store all rotations arr = [0] * n # Create a concatenation of string with itself concat = str_ + str_ # One by one store all rotations of str in array. # A rotation is obtained by getting a substring of concat for i in range(n) : arr[i] = concat[i : n + i] # Sort all rotations arr.sort() # Return the first rotation from the sorted array return arr[0] # Driver Codeprint(minLexRotation("GEEKSFORGEEKS"))print(minLexRotation("GEEKSQUIZ"))print(minLexRotation("BCABDADAB")) # This code is contributed by divyamohan123 |
C#
// A simple C# program to find // lexicographically minimum rotation// of a given Stringusing System; class GFG{ // This functionr return lexicographically // minimum rotation of str static String minLexRotation(String str) { // Find length of given String int n = str.Length; // Create an array of strings // to store all rotations String []arr = new String[n]; // Create a concatenation of // String with itself String concat = str + str; // One by one store all rotations // of str in array. A rotation is // obtained by getting a substring of concat for (int i = 0; i < n; i++) { arr[i] = concat.Substring(i, n); } // Sort all rotations Array.Sort(arr); // Return the first rotation // from the sorted array return arr[0]; } // Driver code public static void Main(String[] args) { Console.WriteLine(minLexRotation("GEEKSFORGEEKS")); Console.WriteLine(minLexRotation("GEEKSQUIZ")); Console.WriteLine(minLexRotation("BCABDADAB")); }} // This code is contributed by Rajput-Ji |
Output:
EEKSFORGEEKSG EEKSQUIZG ABBCABDAD
Lexicographically smallest rotated sequence | Set 2
Time complexity of the above solution is O(n2Logn) under the assumption that we have used a O(nLogn) sorting algorithm.
This problem can be solved using more efficient methods like Booth’s Algorithm which solves the problem in O(n) time. We will soon be covering these methods as separate posts.
This article is contributed by Abhishek. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
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