Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

C++ 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. 

C++




// CPP program to sort all elements except
// element at index k.
#include <bits/stdc++.h>
using namespace std;
  
int sortExceptK(int arr[], int k, int n)
{
    // Move k-th element to end
    swap(arr[k], arr[n-1]);
  
    // Sort all elements except last
    sort(arr, arr + 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;
}
  
// Driver code
int main()
{
    int a[] = {10, 4, 11, 7, 6, 20 };
    int k = 2;
    int n = sizeof(a) / sizeof(a[0]);
    sortExceptK(a, k, n);
    for (int i = 0; i < n; i++)
        cout << a[i] << " ";
}
Output: 
4 6 11 7 10 20 

 

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

My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!