LeetCode Rotate Image

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?

class Solution {

public:

    void rotate(vector<vector<int> > &matrix) {

        int n = matrix.size();

        int end = n / 2;

        for (int i=0; i<end; i++) {

            for (int j=i; j < n - i - 1; j++) {

                int a = matrix[i][j];

                int b = matrix[j][n-1-i];

                int c = matrix[n-1-i][n-1-j];

                int d = matrix[n-1-j][i];

                matrix[i][j] = d;

                matrix[j][n-1-i] = a;

                matrix[n-1-i][n-1-j] = b;

                matrix[n-1-j][i] = c;

            }

        }

    }

};

水一发

更简单的方法：

class Solution {

public:

    void rotate(vector<vector<int> > &matrix) {

        int n = matrix.size();

        for (int i=0; i<n; i++) {

            for (int j=0; j<i; j++) {

                swap(matrix[i][j], matrix[j][i]);

            }

        }

        for (int i=0; i<n; i++) {

            reverse(matrix[i].begin(), matrix[i].end());

        }

    }

};