Sort an almost sorted array where only two elements are swapped

By | November 17, 2021
Sort an almost sorted array where only two elements are swapped

Problem

How can an almost-sorted array with only two members swapped be effectively sorted?

Sample Input

[1, 5, 3]

Sample Output

[1, 3, 5]

Explanation

3 and 5 got swapped

Approach

The goal is to go from right to left and discover the first out-of-order number (a number that is smaller than the previous number). Once the first number is located, traverse the array toward the left side to find the other out-of-order element.

The approach takes O(N) time.

C++ Programming

#include<iostream>
#include<algorithm>
using namespace std;

//function to sort an array
void sortArray(int arr[], int n)
{
    // Traverse the given array from right side
    for (int i = n-1; i > 0; i--)
    {
        // if arr[i] is not in order
        if (arr[i] < arr[i-1])
        {
            int j = i-1;
            while (j>=0 && arr[i] < arr[j])
                j--;
            swap(arr[i], arr[j+1]);
            break;
        }
    }
}
int main()
{
    int arr[] = {1, 5, 3};
    int n = sizeof(arr)/sizeof(arr[0]);


    sortArray(arr, n);

    for(int i=0;i<n;i++) cout<<arr[i]<<" ";
    return 0;
}

Output

1 3 5

C Programming

#include<stdio.h>

//function to sort an array
void sortArray(int arr[], int n)
{
    // Traverse the given array from right side
    for (int i = n-1; i > 0; i--)
    {
        // if arr[i] is not in order
        if (arr[i] < arr[i-1])
        {
            int j = i-1;
            while (j>=0 && arr[i] < arr[j])
                j--;
            int temp = arr[i];  //swap the elements
            arr[i] = arr[j+1];
            arr[j+1] = temp;
            break;
        }
    }
}
void main()
{
    int arr[] = {1, 5, 3};
    int n = sizeof(arr)/sizeof(arr[0]);

    sortArray(arr, n);
    for(int i=0;i<n;i++) printf("%d ",arr[i]);
}

Output

Vamware
1 3 5

Java Programming

import java.io.*;

class Solution
{
//function to sort 
static void sortArray(int arr[], int n)
{
   // Traverse the given array
   // from right side
   for (int i = n - 1; i > 0; i--)
   {
     // if arr[i]
     // is not in order
     if (arr[i] < arr[i - 1])
     {
       // find the other element
       // to be swapped with arr[i]
       int j = i - 1;
       while (j >= 0 && arr[i] < arr[j])
           j--;
      // Swap 
      int temp = arr[i];
      arr[i] = arr[j + 1];
      arr[j + 1] = temp;
     
      break;
     }
   }
}

public static void main(String[] args)
{
   int arr[] = {1, 5, 3};
   int n = arr.length;
   
   sortArray(arr, n);

   for (int i = 0; i < n; i++)
      System.out.print(arr[i] + " ");
    System.out.println();
}
}

Output

1 3 5

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Vamware
Author: Vinay

I am a Full Stack Developer with a Bachelor's Degree in Computer Science, who also loves to write technical articles that can help fellow developers.

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