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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?
先按145°对角线将图像对称翻转, 再将各行逆序翻转即可
class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        int n = matrix.size();
        for (int y = 1; y < n; y++)
            for (int x = 0; x < y; x++)
                swap(matrix[y][x], matrix[x][y]);
                
        for (auto& sub : matrix)
            reverse(sub.begin(), sub.end());
    }
};
原文:http://www.cnblogs.com/ydlme/p/4586999.html