题解 | 顺时针打印矩阵

class Solution {
public:
    vector<int> printMatrix(vector<vector<int> > matrix) {

        int left = 0;
        int right = matrix[0].size() - 1;
        int up = 0;
        int down = matrix.size() - 1;
        vector<int> res;
        while(left <= right && up <= down){
            for(int i = left; i <= right; i ++){
                res.push_back(matrix[up][i]);
            }
            for(int i = up + 1; i <= down; i++){
                res.push_back(matrix[i][right]);
            }
            for(int i = right - 1; i >= left && up < down; i --){
                res.push_back(matrix[down][i]);
            }
            for(int i = down - 1; i > up && left < right; i --){
                res.push_back(matrix[i][left]);
            }
            left++;
            right--;
            up++;
            down--;
        }
        return res;
    }
};