class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {
        vector<int> res;
        int n = matrix.size();
        if(n == 0)  return res;
        int m = matrix[0].size();
        int cnt = 1, i, j;
        i = j = 0;
        bool flag[n][m];

        memset(flag, false, sizeof flag);
        while(cnt <= m * n){
            while(j < m && !flag[i][j]){
                res.push_back(matrix[i][j]);
                flag[i][j ++ ] = true;
                cnt ++ ;
            }
            j -- , i ++ ;
            while(i < n && !flag[i][j]){
                res.push_back(matrix[i][j]);
                flag[i ++ ][j] = true;
                cnt ++ ;
            }
            i -- , j -- ;
            while(j >= 0 && !flag[i][j]){
                res.push_back(matrix[i][j]);
                flag[i][j -- ] = true;
                cnt ++ ;
            }
            j ++ , i -- ;
            while(i >= 0 && !flag[i][j]){
                res.push_back(matrix[i][j]);
                flag[i -- ][j] = true;
                cnt ++ ;
            }
            i ++, j ++ ;
        }
        return res;
    }
};