LeetCode 题解（30）: Rotate Image

题目：

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?

题解：

如此简单的一道题竟然搞了好多错误。一个是offset要注意，一个是内循环次数要注意。

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        for(int i = 0; i < matrix.size() / 2; i++)
        {
            int start = i;
            int end = matrix.size()-1-i;
            for(int j = start; j < end; j++)
            {
                int offset = j - start;
				int temp = matrix[i][j];
                matrix[i][j] = matrix[end-offset][i];
                matrix[end-offset][i] = matrix[end][end-offset];
                matrix[end][end-offset] = matrix[j][end];
                matrix[j][end] = temp;
            }
        }
    }
};