leetcode009-Rotate Image

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

Rotate the image by 90 degrees (clockwise).

Note:
You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = [  [1,2,3],  [4,5,6],  [7,8,9]],rotate the input matrix in-place such that it becomes:[  [7,4,1],  [8,5,2],  [9,6,3]]

Example 2:

Given input matrix =[  [ 5, 1, 9,11],  [ 2, 4, 8,10],  [13, 3, 6, 7],  [15,14,12,16]], rotate the input matrix in-place such that it becomes:[  [15,13, 2, 5],  [14, 3, 4, 1],  [12, 6, 8, 9],  [16, 7,10,11]]

基本思路：这题我尝试了单纯模拟旋转的方法，一圈转完再转里面一圈，思路不复杂，就是找规律。

class Solution {public:    void rotate(vector<vector<int>>& matrix) {        int n = matrix.size();        if (n == 0 || n == 1) return;        int k = 0;        while (1) {            int step = n-1-k*2; //多少圈            if (step <= 0) break;            int i;            for (i = k; i < n-1-k; i++) { // 每一圈内交替交换位置的元素为一组，这里循环圈内的组                int temp = matrix[k][i];                int w = n-1-k-(i);                int h = step-w;                swap(temp,matrix[k+h][i+w]);                swap(temp,matrix[k+h+w][i+w-h]);                swap(temp,matrix[k+w][i-h]);                swap(temp,matrix[k][i]);            }            k++;        }    }     void swap(int& a, int& b) {        a = a^b;        b = a^b;        a = a^b;    }};

Seen this question in a real interview