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Minimize swaps required to place largest and smallest array elements at first and last array indices
  • Difficulty Level : Medium
  • Last Updated : 06 May, 2021

Given an array arr[] of size N, the task is to find the minimum count of adjacent swaps required to rearrange the array elements such that the largest and the smallest array element present on the first and the last indices of the array respectively.

Examples:

Input: arr[] = {33, 44, 11, 12} 
Output:
Explanation: 
Swapping the pair (arr[0], arr[1]) modifies arr[] to {44, 33, 11, 12} 
Swapping the pair (arr[2], arr[3]) modifies arr[] to {44, 33, 12, 11} 
Therefore, the required output is 2. 
 

Input: arr[]={11, 12, 58, 1, 78, 40, 76} 
Output: 6

Approach: Follow the steps below to solve the problem:



  • Traverse the array and calculate the index of the first occurrence of the largest array element say, X, and the last occurrence of the smallest array element say, Y.
  • The count of adjacent swaps required to move the largest array element at the first index is equal to X.
  • The count of adjacent swaps required to move the smallest array element at the last index is equal to N – 1 – Y.
  • If X > Y, then one adjacent swap common in moving the largest element at the first index and the smallest element at the last index. Therefore, the total count of adjacent swaps required is equal to X + (N – 1 – Y) – 1.
  • Otherwise, the total count of adjacent swaps required is equal to X + (N – 1 – Y).

Below is the implementation of the above approach:

C++




// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to  find the minimum count of adjacent
// swaps to move largest and smallest element at the
// first and the last index of the array, respectively
int minimumMoves(int* a, int n)
{
 
    // Stores the smallest array element
    int min_element = INT_MAX;
 
    // Stores the smallest array element
    int max_element = INT_MIN;
 
    // Stores the last occurrence of
    // the smallest array element
    int min_ind = -1;
 
    // Stores the first occurrence of
    // the largest array element
    int max_ind = -1;
 
    // Traverse the array arr[]
    for (int i = 0; i < n; i++) {
 
        // If a[i] is less than
        // min_element
        if (a[i] <= min_element) {
 
            // Update min_element
            min_element = a[i];
 
            // Update min_ind
            min_ind = i;
        }
 
        // If a[i] is greater than
        // max_element
        if (a[i] > max_element) {
 
            // Update max_element
            max_element = a[i];
 
            // Update max_ind
            max_ind = i;
        }
    }
 
    // If max_ind is equal
    // to min_ind
    if (max_ind == min_ind) {
        // Return 0
        return 0;
    }
 
    // If max_ind is greater than min_ind
    else if (max_ind > min_ind) {
 
        return max_ind + (n - min_ind - 2);
    }
 
    // Otherwise
    else {
 
        return max_ind + n - min_ind - 1;
    }
}
 
// Driver Code
int main()
{
 
    // Input
    int arr[] = { 35, 46, 17, 23 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Print the result
    cout << minimumMoves(arr, N) << endl;
}

Java




// Java program for the above approach
import java.util.*;
 
class GFG
{
 
// Function to  find the minimum count of adjacent
// swaps to move largest and smallest element at the
// first and the last index of the array, respectively
static int minimumMoves(int []a, int n)
{
 
    // Stores the smallest array element
    int min_element = Integer.MAX_VALUE;
 
    // Stores the smallest array element
    int max_element = Integer.MIN_VALUE;
 
    // Stores the last occurrence of
    // the smallest array element
    int min_ind = -1;
 
    // Stores the first occurrence of
    // the largest array element
    int max_ind = -1;
 
    // Traverse the array arr[]
    for (int i = 0; i < n; i++)
    {
 
        // If a[i] is less than
        // min_element
        if (a[i] <= min_element)
        {
 
            // Update min_element
            min_element = a[i];
 
            // Update min_ind
            min_ind = i;
        }
 
        // If a[i] is greater than
        // max_element
        if (a[i] > max_element) {
 
            // Update max_element
            max_element = a[i];
 
            // Update max_ind
            max_ind = i;
        }
    }
 
    // If max_ind is equal
    // to min_ind
    if (max_ind == min_ind) {
        // Return 0
        return 0;
    }
 
    // If max_ind is greater than min_ind
    else if (max_ind > min_ind) {
 
        return max_ind + (n - min_ind - 2);
    }
 
    // Otherwise
    else {
 
        return max_ind + n - min_ind - 1;
    }
}
 
// Driver Code
public static void main(String[] args)
{
 
    // Input
    int arr[] = { 35, 46, 17, 23 };
    int N = arr.length;
 
    // Print the result
    System.out.print(minimumMoves(arr, N) +"\n");
}
}
 
// This code is contributed by 29AjayKumar

Python3




# Python 3 program for the above approach
import sys
 
# Function to  find the minimum count of adjacent
# swaps to move largest and smallest element at the
# first and the last index of the array, respectively
def minimumMoves(a, n):
   
    # Stores the smallest array element
    min_element = sys.maxsize
 
    # Stores the smallest array element
    max_element = -sys.maxsize - 1
 
    # Stores the last occurrence of
    # the smallest array element
    min_ind = -1
 
    # Stores the first occurrence of
    # the largest array element
    max_ind = -1
 
    # Traverse the array arr[]
    for i in range(n):
       
        # If a[i] is less than
        # min_element
        if (a[i] <= min_element):
           
            # Update min_element
            min_element = a[i]
 
            # Update min_ind
            min_ind = i
 
        # If a[i] is greater than
        # max_element
        if (a[i] > max_element):
           
            # Update max_element
            max_element = a[i]
 
            # Update max_ind
            max_ind = i
 
    # If max_ind is equal
    # to min_ind
    if (max_ind == min_ind):
       
        # Return 0
        return 0
 
    # If max_ind is greater than min_ind
    elif(max_ind > min_ind):
        return max_ind + (n - min_ind - 2)
 
    # Otherwise
    else:
        return max_ind + n - min_ind - 1
 
# Driver Code
if __name__ == '__main__':
   
    # Input
    arr =  [35, 46, 17, 23]
    N = len(arr)
 
    # Print the result
    print(minimumMoves(arr, N))
 
    # This code is contributed by SURENDRA_GANGWAR.

C#




// C# program for the above approach
using System;
public class GFG
{
 
  // Function to  find the minimum count of adjacent
  // swaps to move largest and smallest element at the
  // first and the last index of the array, respectively
  static int minimumMoves(int []a, int n)
  {
 
    // Stores the smallest array element
    int min_element = int.MaxValue;
 
    // Stores the smallest array element
    int max_element = int.MinValue;
 
    // Stores the last occurrence of
    // the smallest array element
    int min_ind = -1;
 
    // Stores the first occurrence of
    // the largest array element
    int max_ind = -1;
 
    // Traverse the array []arr
    for (int i = 0; i < n; i++)
    {
 
      // If a[i] is less than
      // min_element
      if (a[i] <= min_element)
      {
 
        // Update min_element
        min_element = a[i];
 
        // Update min_ind
        min_ind = i;
      }
 
      // If a[i] is greater than
      // max_element
      if (a[i] > max_element)
      {
 
        // Update max_element
        max_element = a[i];
 
        // Update max_ind
        max_ind = i;
      }
    }
 
    // If max_ind is equal
    // to min_ind
    if (max_ind == min_ind)
    {
 
      // Return 0
      return 0;
    }
 
    // If max_ind is greater than min_ind
    else if (max_ind > min_ind)
    {
      return max_ind + (n - min_ind - 2);
    }
 
    // Otherwise
    else
    {
      return max_ind + n - min_ind - 1;
    }
  }
 
  // Driver Code
  public static void Main(String[] args)
  {
 
    // Input
    int []arr = { 35, 46, 17, 23 };
    int N = arr.Length;
 
    // Print the result
    Console.Write(minimumMoves(arr, N) +"\n");
  }
}
 
// This code is contributed by 29AjayKumar

Javascript




<script>
// javascript program of the above approach
 
// Function to  find the minimum count of adjacent
// swaps to move largest and smallest element at the
// first and the last index of the array, respectively
function minimumMoves(a, n)
{
 
    // Stores the smallest array element
    let min_element = Number.MAX_VALUE;
 
    // Stores the smallest array element
    let max_element = Number.MIN_VALUE;
 
    // Stores the last occurrence of
    // the smallest array element
    let min_ind = -1;
 
    // Stores the first occurrence of
    // the largest array element
    let max_ind = -1;
 
    // Traverse the array arr[]
    for (let i = 0; i < n; i++)
    {
 
        // If a[i] is less than
        // min_element
        if (a[i] <= min_element)
        {
 
            // Update min_element
            min_element = a[i];
 
            // Update min_ind
            min_ind = i;
        }
 
        // If a[i] is greater than
        // max_element
        if (a[i] > max_element) {
 
            // Update max_element
            max_element = a[i];
 
            // Update max_ind
            max_ind = i;
        }
    }
 
    // If max_ind is equal
    // to min_ind
    if (max_ind == min_ind) {
        // Return 0
        return 0;
    }
 
    // If max_ind is greater than min_ind
    else if (max_ind > min_ind) {
 
        return max_ind + (n - min_ind - 2);
    }
 
    // Otherwise
    else {
 
        return max_ind + n - min_ind - 1;
    }
}
 
    // Driver Code
     
       // Input
    let arr = [ 35, 46, 17, 23 ];
    let N = arr.length;
 
    // Prlet the result
    document.write(minimumMoves(arr, N) +"\n");
 
</script>
Output: 
2

 

Time Complexity: O(N)
Auxiliary Space: O(1)

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