每日算法之三十七：Rotate Image （圖像旋轉）

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?

原地圖像順時針旋轉90度。因為要求空間復雜度是常數，因此應該迭代旋轉操作。

class Solution {
public:
    void rotate(vector > &matrix) {
        int n = matrix.size();
        int layers = n/2;//圖像旋轉的圈數
        
        for(int layer = 0;layer < layers;layer++)//每次循環一層，右青色到紫色
         for(int i = layer;i

下面是網友給出的另一種方案：






class Solution {
public:
    void rotate(vector > &matrix) {
        int i,j,temp;
        int n=matrix.size();
        // 沿著副對角線反轉
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n - i; ++j) {
                temp = matrix[i][j];
                matrix[i][j] = matrix[n - 1 - j][n - 1 - i];
                matrix[n - 1 - j][n - 1 - i] = temp;
            }
        }
        // 沿著水平中線反轉
        for (int i = 0; i < n / 2; ++i){
            for (int j = 0; j < n; ++j) {
                temp = matrix[i][j];
                matrix[i][j] = matrix[n - 1 - i][j];
                matrix[n - 1 - i][j] = temp;
            }
        }
    }
};