Rotate Image

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

Rotate the image by 90 degrees (clockwise).

1、对角翻转加上上下翻转

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

2、建立临时矩阵， 直接旋转得到矩阵

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