Replace every element with the smallest of the others

Given an array arr[] of N distinct integers, the task is to replace every element by smallest among all other remaining elements of the array.

Examples:

Input: arr[] = { 4, 2, 1, 3 }
Output: arr[]= { 1, 1, 2, 1 }
Explanation:
For arr[0], the smallest out of the remaining elements is 1. So arr[0] is replaced by 1.
For arr[1], the smallest out of the remaining elements is 1. So arr[1] is replaced by 1.
For arr[2], the smallest out of the remaining elements is 2. So arr[2] is replaced by 2.
For arr[3], the smallest out of the remaining elements is 1. So arr[3] is replaced by 1.

Input: arr[] = { 1, 5, 2, 4 }
Output: arr[] = { 2, 1, 1, 1 }

Naive Approach:
Run a nested loop and find the smallest of all other elements for every single element and store them.
Time Complexity: O(N2)



Efficient Approach:

  1. Traverse the array and find the two smallest elements of the array.
  2. Traverse the array again, now replace the smallest element with the second smallest element and replace every other element in the array with the smallest element.
  3. Print the modified array.

Below is the implementation of above approach:

C++

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// C# implementation to find the 
// maximum array sum by concatenating 
// corresponding elements of given two arrays 
using System;
class GFG{
  
// Function to join the two numbers 
static int joinNumbers(int numA, int numB)
{
    int revB = 0;
  
    // Loop to reverse the digits 
    // of the one number 
    while (numB > 0)
    {
        revB = revB * 10 + (numB % 10);
        numB = numB / 10;
    }
  
    // Loop to join two numbers 
    while (revB > 0)
    {
        numA = numA * 10 + (revB % 10);
        revB = revB / 10;
    }
  
    return numA;
}
  
// Function to find the maximum array sum 
static int findMaxSum(int []A, int []B, int n)
{
    int []maxArr = new int[n];
  
    // Loop to iterate over the two 
    // elements of the array 
    for(int i = 0; i < n; ++i)
    {
        int X = joinNumbers(A[i], B[i]);
        int Y = joinNumbers(B[i], A[i]);
        int mx = Math.Max(X, Y);
      
        maxArr[i] = mx;
    }
  
    // Find the array sum 
    int maxAns = 0;
    for(int i = 0; i < n; i++)
    {
        maxAns += maxArr[i];
    }
  
    // Return the array sum 
    return maxAns;
}
  
// Driver Code
public static void Main(String []args)
{
    int N = 5;
    int []A = { 11, 23, 38, 43, 59 };
    int []B = { 36, 24, 17, 40, 56 };
  
    Console.WriteLine(findMaxSum(A, B, N));
}
}
  
// This code is contributed by Rajput-Ji

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Java

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// Java code for the above approach.
import java.util.*;
  
class GFG {
  
    static void ReplaceElements(
        int[] arr, int n)
    {
  
        // There should be atleast
        // two elements
        if (n < 2) {
  
            System.out.println(
                "Invalid Input");
  
            return;
        }
  
        int firstSmallest
            = Integer.MAX_VALUE;
        int secondSmallest
            = Integer.MAX_VALUE;
  
        for (int i = 0; i < n; i++) {
  
            // If current element is smaller
            // than firstSmallest then update
            // both firstSmallest
            // and secondSmallest
            if (arr[i] < firstSmallest) {
  
                secondSmallest = firstSmallest;
                firstSmallest = arr[i];
            }
  
            // If arr[i] is in between
            // firstSmallest and secondSmallest
            // then update secondSmallest
            else if (arr[i] < secondSmallest
                     && arr[i] != firstSmallest)
                secondSmallest = arr[i];
        }
  
        // Replace every element by
        // smallest of all other elements
        for (int i = 0; i < n; i++) {
  
            if (arr[i] != firstSmallest)
                arr[i] = firstSmallest;
  
            else
                arr[i] = secondSmallest;
        }
  
        // Print the modified array.
        for (int i = 0; i < n; ++i) {
            System.out.print(arr[i]
                             + ", ");
        }
    }
  
    // Driver code
    public static void main(
        String[] args)
    {
        int arr[] = { 4, 2, 1, 3 };
        int n = arr.length;
  
        ReplaceElements(arr, n);
    }
}

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Python3

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# Python3 code for the above approach.
def ReplaceElements(arr, n):
  
    # There should be atleast
    # two elements
    if (n < 2):
        print("Invalid Input")
        return
  
    firstSmallest = 10 ** 18
    secondSmallest = 10 ** 18
  
    for i in range(n):
  
        # If current element is smaller
        # than firstSmallest then update
        # both firstSmallest
        # and secondSmallest
        if (arr[i] < firstSmallest):
            secondSmallest = firstSmallest
            firstSmallest = arr[i]
  
        # If arr[i] is in between
        # firstSmallest and secondSmallest
        # then update secondSmallest
        elif (arr[i] < secondSmallest and
              arr[i] != firstSmallest):
            secondSmallest = arr[i]
  
    # Replace every element by
    # smallest of all other elements
    for i in range(n):
  
        if (arr[i] != firstSmallest):
            arr[i] = firstSmallest
  
        else:
            arr[i] = secondSmallest
  
    # Print the modified array.
    for i in arr:
        print(i, end = ", ")
  
  
# Driver code
if __name__ == '__main__':
       
    arr= [ 4, 2, 1, 3 ]
    n = len(arr)
  
    ReplaceElements(arr, n)
  
# This code is contributed by mohit kumar 29

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C#

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// C# code for the above approach.
using System;
  
class GFG{
  
static void ReplaceElements(int[] arr, int n)
{
  
    // There should be atleast
    // two elements
    if (n < 2) 
    {
        Console.Write("Invalid Input");
  
        return;
    }
  
    int firstSmallest = Int32.MaxValue;
    int secondSmallest = Int32.MaxValue;
  
    for(int i = 0; i < n; i++) 
    {
         
       // If current element is smaller
       // than firstSmallest then update
       // both firstSmallest
       // and secondSmallest
       if (arr[i] < firstSmallest) 
       {
           secondSmallest = firstSmallest;
           firstSmallest = arr[i];
       }
         
       // If arr[i] is in between
       // firstSmallest and secondSmallest
       // then update secondSmallest
       else if (arr[i] < secondSmallest &&
                arr[i] != firstSmallest)
           secondSmallest = arr[i];
    }
  
    // Replace every element by
    // smallest of all other elements
    for(int i = 0; i < n; i++) 
    {
       if (arr[i] != firstSmallest)
           arr[i] = firstSmallest;
       else
           arr[i] = secondSmallest;
    }
  
    // Print the modified array.
    for(int i = 0; i < n; ++i) 
    {
       Console.Write(arr[i] + ", ");
    }
}
  
// Driver code
public static void Main()
{
    int []arr = { 4, 2, 1, 3 };
    int n = arr.Length;
  
    ReplaceElements(arr, n);
}
}
  
// This code is contributed by Nidhi_Biet

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Output:

1, 1, 2, 1,


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

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