161. Rotate Image

Code(Language:C++) (Judger:cloudjudge-cluster-5)

class Solution {
public:
    /**
     * @param matrix: a lists of integers
     * @return: nothing
     */
    void rotate(vector<vector<int>> &matrix) {
        // write your code here
        const int n = matrix.size();
        if(n <= 1){
            return; 
        }
        int cnt = 0; 
        // (n - 1, 0) -> (0, 0); (n - 1, n - 1) -> (n - 1, 0); (0, n - 1) -> (n - 1, n - 1); (0, 0) -> (0, n - 1); 
        while((cnt + 1) * 2 <= n){
            for(int j = cnt; j < n - cnt - 1; j++){ //注意这里，不是n - cnt, 一行的最后一个不用处理
               int tmp = matrix[cnt][j];
               matrix[cnt][j] = matrix[n - 1 - j][cnt];
               matrix[n - 1 - j][cnt] = matrix[n - 1 - cnt][n - 1 - j]; 
               matrix[n - 1 - cnt][n - 1 - j] = matrix[j][n - 1 - cnt]; 
               matrix[j][n - 1 - cnt] = tmp; 
            }
            cnt++; 
        }
        return; 
    }
};

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