Program to Interchange Diagonals of Matrix

Given a square matrix of order n*n, you have to interchange the elements of both diagonals. 

Examples :

Input : matrix[][] = {1, 2, 3,
                      4, 5, 6,
                      7, 8, 9} 
Output : matrix[][] = {3, 2, 1,
                       4, 5, 6,
                       9, 8, 7} 

Input : matrix[][] = {4,  2,  3,  1,
                      5,  7,  6,  8,
                      9, 11, 10, 12,
                     16, 14, 15, 13} 
Output : matrix[][] = {1,  2,  3,  4,
                       5,  6,  7,  8,
                       9, 10, 11, 12,
                      11, 14, 15, 16}

Explanation : Idea behind interchanging diagonals of a square matrix is simple. Iterate from 0 to n-1 and for each iteration you have to swap a[i][i] and a[i][n-i-1].

Implementation:

C++

// C++ program to interchange
// the diagonals of matrix
#include<bits/stdc++.h>
using namespace std;

#define N 3

// Function to interchange diagonals
void interchangeDiagonals(int array[][N])
{
    // swap elements of diagonal
    for (int i = 0; i < N; ++i)
    if (i != N / 2)
    swap(array[i][i], array[i][N - i - 1]);

    for (int i = 0; i < N; ++i)
    {
    for (int j = 0; j < N; ++j)
            cout<<" "<< array[i][j];
    cout<<endl;
    }
}

// Driver Code
int main()
{
    int array[N][N] = {4, 5, 6,
                    1, 2, 3,
                    7, 8, 9};
    interchangeDiagonals(array);
    return 0;
}

// This code is contributed by noob2000.

C

// C program to interchange
// the diagonals of matrix
#include<bits/stdc++.h>
using namespace std;

#define N 3

// Function to interchange diagonals
void interchangeDiagonals(int array[][N])
{
    // swap elements of diagonal
    for (int i = 0; i < N; ++i)
    if (i != N / 2)
    swap(array[i][i], array[i][N - i - 1]);

    for (int i = 0; i < N; ++i)
    {
    for (int j = 0; j < N; ++j)
            printf(" %d", array[i][j]);
    printf("\n");
    }
}

// Driver Code
int main()
{
    int array[N][N] = {4, 5, 6,
                    1, 2, 3,
                    7, 8, 9};
    interchangeDiagonals(array);
    return 0;
}

Java

// Java program to interchange
// the diagonals of matrix
import java.io.*;

class GFG
{
    public static int N = 3;

    // Function to interchange diagonals
    static void interchangeDiagonals(int array[][])
    {
        // swap elements of diagonal
        for (int i = 0; i < N; ++i)
            if (i != N / 2)
            {
                int temp = array[i][i];
                array[i][i] = array[i][N - i - 1];
                array[i][N - i - 1] = temp;
            }

        for (int i = 0; i < N; ++i)
        {
            for (int j = 0; j < N; ++j)
                System.out.print(array[i][j]+" ");
            System.out.println();
        }
    }

    // Driver Code
    public static void main (String[] args)
    {
        int array[][] = { {4, 5, 6},
                        {1, 2, 3},
                        {7, 8, 9}
                        };
        interchangeDiagonals(array);
    }
}

// This code is contributed by Pramod Kumar

Python3

# Python program to interchange
# the diagonals of matrix
N = 3;

# Function to interchange diagonals
def interchangeDiagonals(array):

    # swap elements of diagonal
    for i in range(N):
        if (i != N / 2):
            temp = array[i][i];
            array[i][i] = array[i][N - i - 1];
            array[i][N - i - 1] = temp;

    for i in range(N):
        for j in range(N):
            print(array[i][j], end = " ");
        print();

# Driver Code
if __name__ == '__main__':
    array = [ 4, 5, 6 ],[ 1, 2, 3 ],[ 7, 8, 9 ];
    interchangeDiagonals(array);

# This code is contributed by Rajput-Ji

C#

// C# program to interchange
// the diagonals of matrix
using System;

class GFG
{
    public static int N = 3;

    // Function to interchange diagonals
    static void interchangeDiagonals(int [,]array)
    {
        // swap elements of diagonal
        for (int i = 0; i < N; ++i)
            if (i != N / 2)
            {
                int temp = array[i, i];
                array[i, i] = array[i, N - i - 1];
                array[i, N - i - 1] = temp;
            }

        for (int i = 0; i < N; ++i)
        {
            for (int j = 0; j < N; ++j)
                Console.Write(array[i, j]+" ");
            Console.WriteLine();
        }
    }

    // Driver Code
    public static void Main ()
    {
        int [,]array = { {4, 5, 6},
                        {1, 2, 3},
                        {7, 8, 9}
                        };
        interchangeDiagonals(array);
    }
}

// This code is contributed by vt_m.

Javascript

<script>
// Javascript program to interchange
// the diagonals of matrix
let N = 3;

// Function to interchange diagonals
function interchangeDiagonals(array)
{

    // swap elements of diagonal
    for (let i = 0; i < N; ++i)
    if (i != parseInt(N / 2)) {
        let temp = array[i][i];
        array[i][i] = array[i][N - i - 1];
        array[i][N - i - 1] = temp;
    }
    for (let i = 0; i < N; ++i)
    {
    for (let j = 0; j < N; ++j)
            document.write(" " + array[i][j]);
    document.write("<br>");
    }
}

// Driver Code
    let array = [[4, 5, 6],
                    [1, 2, 3],
                    [7, 8, 9]];
    interchangeDiagonals(array);

// This code is contributed by subham348.
</script>

Output

 6 5 4
 1 2 3
 9 8 7

Time Complexity: O(N*N), as we are using nested loops for traversing the matrix.
Auxiliary Space: O(1), as we are not using any extra space.

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