Sorting all array elements except one
Last Updated :
11 Jul, 2025
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.
- Swap k-th element with the last element.
- Sort all elements except the last.
- For every element from (k+1)-th to last, move them one position ahead.1
- 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] << " ";
}
// 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.
# Python3 program to sort all elements except
# element at index k.
def sortExcept(arr, k, n):
# Move k-th element to end
arr[k], arr[-1] = arr[-1], arr[k]
# Sort all elements except last
arr = sorted(arr, key = lambda i: (i is arr[-1], i))
# Store last element (originally k-th)
last = arr[-1]
# Move all elements from k-th to one
# position ahead.
i = n - 1
while i > k:
arr[i] = arr[i - 1]
i -= 1
# Restore k-th element
arr[k] = last
return arr
# Driver code
if __name__ == '__main__':
a = [10, 4, 11, 7, 6, 20]
k = 2
n = len(a)
a = sortExcept(a, k, n)
print(" ".join(list(map(str, a))))
# This code is contributed by Shivam Singh.
// C# program to sort all elements except
// element at index k.
using System;
public 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
Array.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()
{
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++)
Console.Write(a[i] + " ");
}
}
// This article is contributed by shiv_bhakt
<?php
// PHP program to sort all
// elements except element
// at index k.
function sortExceptK(&$arr, $k, $n)
{
// Move k-th element to end
$t = $arr[$k];
$arr[$k] = $arr[$n - 1];
$arr[$n - 1] = $t;
// Sort all elements
// except last
$t = $arr[count($arr) - 1];
$arr = array_slice($arr, 0, -1);
sort($arr);
array_push($arr, $t);
// Store last element
// (originally k-th)
$last = $arr[$n - 1];
// Move all elements from
// k-th to one position ahead.
for ($i = $n - 1; $i > $k; $i--)
$arr[$i] = $arr[$i - 1];
// Restore k-th element
$arr[$k] = $last;
}
// Driver code
$a = array(10, 4, 11,
7, 6, 20 );
$k = 2;
$n = count($a);
sortExceptK($a, $k, $n);
for ($i = 0; $i < $n; $i++)
echo ($a[$i]." ");
// This code is contributed by
// Manish Shaw(manishshaw1)
?>
<script>
// Javascript program to sort all elements except
// element at index k.
function sortExceptK(arr, k, n)
{
// Move k-th element to end
let temp = arr[k];
arr[k] = arr[n-1];
arr[n-1] = temp;
// Sort all elements except last
arr.sort(function(a, b){
return a - b});
// Store last element (originally k-th)
let last = arr[n-1];
// Move all elements from k-th to one
// position ahead.
for (let i = n-1; i > k; i--)
arr[i] = arr[i-1];
// Restore k-th element
arr[k] = last;
// Move k-th element to end
temp = arr[k];
arr[k] = arr[n-1];
arr[n-1] = temp;
return 0;
}
let a = [10, 4, 11, 7, 6, 20 ];
let k = 2;
let n = a.length;
sortExceptK(a, k, n);
for(let i = 0; i < n; i++)
document.write(a[i] + " ");
</script>
Time Complexity: O(n*log(n)) where n is the number of elements.
Auxiliary Space: O(1)
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