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Program to Interchange Diagonals of Matrix
  • Difficulty Level : Basic
  • Last Updated : 20 Apr, 2021

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]. 
 

Time complexity : O(n) 
 

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

This article is contributed by Shivam Pradhan (anuj_charm). If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
 




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