LeetCode 48. Rotate Image

题目描述:

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up: Could you do this in-place?

题目要求将一个n*n数组顺时针旋转90度, 并且最好不使用额外空间. 所以用对角线将矩阵分为四个区域, 对于每个区域内的每个元素依次放入上一个区域的值.

class Solution {
public:
    void rotate(vector<vector<int>>& matrix) {
        int n = matrix.size();
        for(int i = 0; i < n / 2; i++){
            for(int j = i; j < n - 1 - i; j++){
                int swap_t = matrix[i][j];
                matrix[i][j] = matrix[n - 1 - j][i];
                matrix[n - 1 - j][i] = matrix[n - 1 - i][n - 1 - j];
                matrix[n - 1 - i][n - 1 - j] = matrix[j][n - 1 - i];
                matrix[j][n - 1 - i] = swap_t;
            }
        }
    }
};