# Swap major and minor diagonals of a square matrix

Given a square matrix, swap the element of major and minor diagonals.

Major Diagonal Elements of a Matrix :

The Major Diagonal Elements are the ones that occur from Top Left of Matrix Down To Bottom Right Corner. The Major Diagonal is also known as Main Diagonal or Primary Diagonal.

Minor Diagonal Elements of a Matrix :

The Minor Diagonal Elements are the ones that occur from Top Right of Matrix Down To Bottom Left Corner. Also known as Secondary Diagonal.

**Example :**

Input: 0 1 2 3 4 5 6 7 8Output :2 1 0 3 4 5 8 7 6

**Approach:** The Simple thing one should know is that the indexes of Primary or Major diagonal are same i.e. lets say A is matrix then A[1][1] will be a Major Diagonal element and sum of indexes of Minor Diagonal is equal to size of Matrix. Lets say A is a matrix of size 3 then A[1][2] will be Minor Diagonal element.

Below is the implementation of above approach :

## C++

`// CPP Program to swap diagonal of a matrix` `#include <bits/stdc++.h>` `using` `namespace` `std;` `// size of square matrix` `#define N 3` `// Function to swap diagonal of matrix` `void` `swapDiagonal(` `int` `matrix[][N]) {` ` ` `for` `(` `int` `i = 0; i < N; i++)` ` ` `swap(matrix[i][i], matrix[i][N - i - 1]);` `}` `// Driver Code` `int` `main() {` ` ` `int` `matrix[N][N] = {{0, 1, 2}, ` ` ` `{3, 4, 5}, ` ` ` `{6, 7, 8}};` ` ` `swapDiagonal(matrix);` ` ` `// Displaying modified matrix` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `for` `(` `int` `j = 0; j < N; j++)` ` ` `cout << matrix[i][j] << ` `" "` `;` ` ` `cout << endl;` ` ` `}` ` ` `return` `0;` `}` |

## Java

`// Java implementation to swap` `// diagonal of a matrix` `import` `java.io.*;` `class` `Gfg {` `static` `int` `N = ` `3` `;` `// Function to swap diagonal of matrix` `static` `void` `swapDiagonal(` `int` `matrix[][]) {` ` ` `for` `(` `int` `i = ` `0` `; i < N; i++) {` ` ` `int` `temp = matrix[i][i];` ` ` `matrix[i][i] = matrix[i][N - i - ` `1` `];` ` ` `matrix[i][N - i - ` `1` `] = temp;` ` ` `}` `}` `// Driver function` `public` `static` `void` `main(String arg[]) {` ` ` `int` `matrix[][] = {{` `0` `, ` `1` `, ` `2` `}, ` ` ` `{` `3` `, ` `4` `, ` `5` `}, ` ` ` `{` `6` `, ` `7` `, ` `8` `}};` ` ` `swapDiagonal(matrix);` ` ` `// Displaying modified matrix` ` ` `for` `(` `int` `i = ` `0` `; i < N; i++) {` ` ` `for` `(` `int` `j = ` `0` `; j < N; j++)` ` ` `System.out.print(matrix[i][j] + ` `" "` `);` ` ` `System.out.println();` ` ` `}` `}` `}` `// This code is contributed by Anant Agarwal.` |

## Python3

`# Python3 Program to swap diagonal of a matrix` `# size of square matrix` `N ` `=` `3` `# Function to swap diagonal of matrix` `def` `swapDiagonal(matrix):` ` ` ` ` `for` `i ` `in` `range` `(N):` ` ` ` ` `matrix[i][i], matrix[i][N` `-` `i` `-` `1` `] ` `=` `\` ` ` `matrix[i][N` `-` `i` `-` `1` `], matrix[i][i]` `# Driver Code` `matrix ` `=` `[[` `0` `, ` `1` `, ` `2` `],` ` ` `[` `3` `, ` `4` `, ` `5` `],` ` ` `[` `6` `, ` `7` `, ` `8` `]]` `# swap diagonals of matrix` `swapDiagonal(matrix);` `# Displaying modified matrix` `for` `i ` `in` `range` `(N): ` ` ` `for` `j ` `in` `range` `(N): ` ` ` `print` `(matrix[i][j], end ` `=` `' '` `) ` ` ` `print` `()` |

## C#

`// C# implementation to swap` `// diagonal of a matrix` `using` `System;` `class` `Gfg {` ` ` ` ` `static` `int` `N = 3;` ` ` ` ` `// Function to swap diagonal of matrix` ` ` `static` `void` `swapDiagonal(` `int` `[,]matrix) {` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `int` `temp = matrix[i,i];` ` ` `matrix[i,i] = matrix[i,N - i - 1];` ` ` `matrix[i,N - i - 1] = temp;` ` ` `}` ` ` `}` ` ` ` ` `// Driver function` ` ` `public` `static` `void` `Main() {` ` ` `int` `[,]matrix = {{0, 1, 2}, ` ` ` `{3, 4, 5}, ` ` ` `{6, 7, 8}};` ` ` ` ` `swapDiagonal(matrix);` ` ` ` ` `// Displaying modified matrix` ` ` `for` `(` `int` `i = 0; i < N; i++) {` ` ` `for` `(` `int` `j = 0; j < N; j++)` ` ` `Console.Write(matrix[i,j] + ` `" "` `);` ` ` `Console.WriteLine();` ` ` `}` ` ` `}` `}` `// This code is contributed by vt_m.` |

## PHP

`<?php` `// PHP Program to swap ` `// diagonal of a matrix` `// size of square matrix` `$N` `= 3;` `// Function to swap ` `// diagonal of matrix` `function` `swapDiagonal(` `$matrix` `) ` `{` ` ` `global` `$N` `;` ` ` `for` `(` `$i` `= 0; ` `$i` `< ` `$N` `; ` `$i` `++)` ` ` `{` ` ` `$tmp` `=` `$matrix` `[` `$i` `][` `$i` `];` ` ` `$matrix` `[` `$i` `][` `$i` `] = ` `$matrix` `[` `$i` `][` `$N` `- ` `$i` `- 1];` ` ` `$matrix` `[` `$i` `][` `$N` `- ` `$i` `- 1] = ` `$tmp` `;` ` ` `}` ` ` `// Displaying modified matrix` `for` `(` `$i` `= 0; ` `$i` `< ` `$N` `; ` `$i` `++) ` `{` ` ` `for` `(` `$j` `= 0; ` `$j` `< ` `$N` `; ` `$j` `++)` ` ` `echo` `$matrix` `[` `$i` `][` `$j` `] . ` `" "` `;` ` ` `echo` `"\n"` `;` `}` `}` `// Driver Code` `$matrix` `= ` `array` `(` `array` `(0, 1, 2), ` ` ` `array` `(3, 4, 5), ` ` ` `array` `(6, 7, 8));` `swapDiagonal(` `$matrix` `);` `// This code is contributed by mits` `?>` |

## Javascript

`<script>` `// JavaScript program to swap` `// diagonal of a matrix.` `// size of square matrix` `let N = 3;` ` ` `// Function to swap diagonal of matrix` `function` `swapDiagonal(matrix) {` ` ` `for` `(let i = 0; i < N; i++) {` ` ` `let temp = matrix[i][i];` ` ` `matrix[i][i] = matrix[i][N - i - 1];` ` ` `matrix[i][N - i - 1] = temp;` ` ` `}` `}` ` ` ` ` `// Driver code` ` ` `let matrix = [[0, 1, 2], ` ` ` `[3, 4, 5], ` ` ` `[6, 7, 8]];` ` ` ` ` `swapDiagonal(matrix);` ` ` ` ` `// Displaying modified matrix` ` ` `for` `(let i = 0; i < N; i++) {` ` ` `for` `(let j = 0; j < N; j++)` ` ` `document.write(matrix[i][j] + ` `" "` `);` ` ` `document.write(` `"<br/>"` `);` ` ` `}` `</script>` |

**Output**

2 1 0 3 4 5 8 7 6

**Time Complexity: O(N*N)**, as we are using nested loops to traverse N*N times.**Auxiliary Space: O(1)**, as we are not using any extra space.