LeetCode(48)RotateImage

题目如下：

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?

分析如下：

比较简单的一道题目。先沿着对角线(左上到右下)做对称变换，然后沿着竖直中心轴做对称变换。

我的代码

class Solution {
public:
    void rotate(vector<vector<int> > &matrix) {
        if(matrix.empty())
            return;
        int n=matrix.size();
        //沿着对角线(左上到右下)做对称变换
        for(int k=0;k<n;k++){
            for(int i=0;i<k;i++){
                int tmp=matrix[k][i];
                matrix[k][i]=matrix[i][k];
                matrix[i][k]=tmp;
            }
        }
        //沿着竖直中心轴做对称变换
        for(int k=0;k<n;k++){
            int s=0;
            int t=n-1;
            while(s<t){
                int tmp=matrix[k][s];
                matrix[k][s]=matrix[k][t];
                matrix[k][t]=tmp;
                s++;
                t--;
            }
        }
        return;
    }
};

update 2014-11-09 和上面思路一样，换了个写法

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