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Java Program to Find Lexicographically minimum string rotation | Set 1

  • Last Updated : 27 Dec, 2021

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. 

Java




// A simple Java program to find 
// lexicographically minimum rotation
// of a given String
import 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


Output: 

EEKSFORGEEKSG
EEKSQUIZG
ABBCABDAD

Time complexity of the above solution is O(n2Logn) under the assumption that we have used a O(nLogn) sorting algorithm. 
Please refer complete article on Lexicographically minimum string rotation | Set 1 for more details!


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