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Interchange elements of first and last rows in matrix

  • Difficulty Level : Basic
  • Last Updated : 06 May, 2021

Given a 4 x 4 matrix, we have to interchange the elements of first and last row and show the resulting matrix.
Examples : 
 

Input : 3 4 5 0
        2 6 1 2
        2 7 1 2
        2 1 1 2
Output : 2 1 1 2
         2 6 1 2
         2 7 1 2
         3 4 5 0

Input : 9 7 5 1
        2 3 4 1
        5 6 6 5
        1 2 3 1
Output : 1 2 3 1
         2 3 4 1
         5 6 6 5
         9 7 5 1

 

The approach is very simple, we can simply swap the elements of first and last row of the matrix inorder to get the desired matrix as output.
Below is the implementation of the approach : 
 

C++




// C++ code to swap the element of first
// and last row and display the result
#include <iostream>
using namespace std;
 
#define n 4
 
void interchangeFirstLast(int m[][n])
{
        int rows = n;
         
        // swapping of element between first
        // and last rows
        for (int i = 0; i < n; i++)
        {
            int t = m[0][i];
            m[0][i] = m[rows - 1][i];
            m[rows - 1][i] = t;
        }
}
 
// Driver function
int main()
{
    // input in the array
    int m[n][n] = { { 8, 9, 7, 6 },
                { 4, 7, 6, 5 },
                { 3, 2, 1, 8 },
                { 9, 9, 7, 7 } };
                 
    interchangeFirstLast(m);
     
    // printing the interchanged matrix
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
            cout << m[i][j] << " ";
        cout << endl;
    }
}
 
// This code is contributed by Anant Agarwal.

Java




// Java code to swap the element of first
// and last row and display the result
import java.io.*;
 
public class Interchange {
     
    static void interchangeFirstLast(int m[][])
    {
        int rows = m.length;
         
        // swapping of element between first
        // and last rows
        for (int i = 0; i < m[0].length; i++) {
            int t = m[0][i];
            m[0][i] = m[rows-1][i];
            m[rows-1][i] = t;
        }
    }
     
    // Driver code
    public static void main(String args[]) throws IOException
    {
        // input in the array
        int m[][] = { { 8, 9, 7, 6 },
                    { 4, 7, 6, 5 },
                    { 3, 2, 1, 8 },
                    { 9, 9, 7, 7 } };
                     
        interchangeFirstLast(m);
         
        // printing the interchanged matrix
        for (int i = 0; i < m.length; i++) {
            for (int j = 0; j < m[0].length; j++)
                System.out.print(m[i][j] + " ");
            System.out.println();
        }
    }
}

Python3




# Python code to swap the element
# of first and last row and display
# the result
 
def interchangeFirstLast(mat, n, m):
    rows = n
     
    # swapping of element between
    # first and last rows
    for i in range(n):
        t = mat[0][i]
        mat[0][i] = mat[rows-1][i]
        mat[rows-1][i] = t
 
# Driver Program
mat = [[8, 9, 7, 6],
          [4, 7, 6, 5],
       [3, 2, 1, 8],
       [9, 9, 7, 7]]
 
n = 4
m = 4
interchangeFirstLast(mat, n, m)
 
# printing the interchanged matrix
for i in range(n):
    for j in range(m):
        print(mat[i][j], end = " ")
    print("\n")
 
# This code is contributed by Shrikant13.

C#




// C# code to swap the element of first
// and last row and display the result
using System;
 
class GFG
{
 
public static void interchangeFirstLast(int[][] m)
{
    int rows = m.Length;
 
    // swapping of element between first
    // and last rows
    for (int i = 0; i < m[0].Length; i++)
    {
        int t = m[0][i];
        m[0][i] = m[rows - 1][i];
        m[rows - 1][i] = t;
    }
}
 
// Driver code
public static void Main(string[] args)
{
    // input in the array
    int[][] m = new int[][]
    {
        new int[] {8, 9, 7, 6},
        new int[] {4, 7, 6, 5},
        new int[] {3, 2, 1, 8},
        new int[] {9, 9, 7, 7}
    };
 
    interchangeFirstLast(m);
 
    // printing the interchanged matrix
    for (int i = 0; i < m.Length; i++)
    {
        for (int j = 0; j < m[0].Length; j++)
        {
            Console.Write(m[i][j] + " ");
        }
        Console.WriteLine();
    }
}
}
 
// This code is contributed by Shrikant13

PHP




<?php
// PHP code to swap the element of first
// and last row and display the result
$n = 4;
 
function interchangeFirstLast(&$m)
{
        global $n;
        $rows = $n;
          
        // swapping of element between first
        // and last rows
        for ($i = 0; $i < $n; $i++)
        {
            $t = $m[0][$i];
            $m[0][$i] = $m[$rows - 1][$i];
            $m[$rows - 1][$i] = $t;
        }
}
  
// Driver function
 
// input in the array
$m = array(array(8, 9, 7, 6),
            array(4, 7, 6, 5),
            array( 3, 2, 1, 8),
            array(9, 9, 7, 7));
              
interchangeFirstLast($m);
  
// printing the interchanged matrix
for ($i = 0; $i < $n; $i++)
{
    for ($j = 0; $j < $n; $j++)
        echo $m[$i][$j] . " ";
    echo "\n";
}
?>

Javascript




<script>
// Javascript code to swap the element of first
// and last row and display the result
     
    function interchangeFirstLast(m)
    {
        let rows = m.length;
           
        // swapping of element between first
        // and last rows
        for (let i = 0; i < m[0].length; i++) {
            let t = m[0][i];
            m[0][i] = m[rows-1][i];
            m[rows-1][i] = t;
        }
    }
     
    // Driver code
     
    // input in the array
    let m = [[8, 9, 7, 6],
          [4, 7, 6, 5],
       [3, 2, 1, 8],
       [9, 9, 7, 7]]
        interchangeFirstLast(m);
           
     // printing the interchanged matrix
     for (let i = 0; i < m.length; i++) {
        for (let j = 0; j < m[0].length; j++)
            document.write(m[i][j] + " ");
        document.write("<br>");
     }
     
     
    // This code is contributed by avanitrachhadiya2155
</script>

Output : 
 

9 9 7 7 
4 7 6 5 
3 2 1 8 
8 9 7 6 

 




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