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Java Program for Sorting all array elements except one

  • Last Updated : 19 Jan, 2022

Given an array, a positive integer, sort the array in ascending order such that the element at index K in the unsorted array stays unmoved and all other elements are sorted. 

Examples: 

Input : arr[] = {10, 4, 11, 7, 6, 20}
            k = 2;
Output : arr[] = {4, 6, 11, 7, 10, 20}

Input : arr[] = {30, 20, 10}
         k = 0
Output : arr[] = {30, 10, 20} 

A simple solution is to copy all elements except k-th of a given array to another array. Then sort the other array using a sorting algorithm. Finally, again copy the sorted array to the original array. While copying, skip k-th element.
 

Below is an efficient solution.  

  1. Swap k-th element with the last element.
  2. Sort all elements except the last.
  3. For every element from (k+1)-th to last, move them one position ahead.1
  4. Copy k-th element back to position k. 

Java




// Java program to sort all elements except
// element at index k.
import java.util.Arrays;
  
class GFG {
      
    static int sortExceptK(int arr[], int k, int n)
    {
          
        // Move k-th element to end
        int temp = arr[k];
        arr[k] = arr[n-1];
        arr[n-1] = temp;
      
        // Sort all elements except last
        Arrays.sort(arr, 0, n-1);
      
        // Store last element (originally k-th)
        int last = arr[n-1];
      
        // Move all elements from k-th to one
        // position ahead.
        for (int i = n-1; i > k; i--)
        arr[i] = arr[i-1];
      
        // Restore k-th element
        arr[k] = last;
        return 0;
    }
      
    //Driver code
    public static void main (String[] args)
    {
        int a[] = {10, 4, 11, 7, 6, 20 };
        int k = 2;
        int n = a.length;
          
        sortExceptK(a, k, n);
          
        for (int i = 0; i < n; i++)
            System.out.print(a[i] + " ");
    }
}
  
//This code is contributed by Anant Agarwal.
Output: 
4 6 11 7 10 20 

 

Please refer complete article on Sorting all array elements except one for more details!


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