# 程序用矩阵的下对角元素交换上对角元素。 > 原文： [https://www.geeksforgeeks.org/program-swap-upper-diagonal-elements-lower-diagonal-elements-matrix/](https://www.geeksforgeeks.org/program-swap-upper-diagonal-elements-lower-diagonal-elements-matrix/) 给定一个正方形矩阵，将矩阵的上对角线元素与矩阵的下对角线元素交换。 **示例**： ``` Input: 2 3 5 6 4 5 7 9 8 6 4 9 1 3 5 6 Output: 2 4 8 1 3 5 6 3 5 7 4 5 6 9 9 6 Input: 1 2 3 4 5 6 7 8 9 Output: 1 4 7 2 5 8 3 6 9 ``` 以下是上述想法的实现： ## C++ ```cpp // CPP Program to implement matrix // for swapping the upper diagonal // elements with lower diagonal  // elements of matrix. #include <bits/stdc++.h> #define n 4 using namespace std; // Function to swap the diagonal  // elements in a matrix. void swapUpperToLower(int arr[n][n]) {     // Loop for swap the elements of matrix.     for (int i = 0; i < n; i++) {         for (int j = i + 1; j < n; j++) {             int temp = arr[i][j];             arr[i][j] = arr[j][i];             arr[j][i] = temp;         }     }     // Loop for print the matrix elements.     for (int i = 0; i < n; i++) {         for (int j = 0; j < n; j++)             cout << arr[i][j] << " ";         cout << endl;     } } // Driver function to run the program int main() {     int arr[n][n] = { { 2, 3, 5, 6 },                     { 4, 5, 7, 9 },                     { 8, 6, 4, 9 },                     { 1, 3, 5, 6 } };     // Function call     swapUpperToLower(arr);     return 0; } } ```