LeetCode 54. 螺旋矩阵

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        vector<int> res;
        int num, n = 0;
        int i = 0, j = 0;
        int left = 0, right = matrix[0].size(), up = 1, down = matrix.size();
        num = matrix.size() * matrix[0].size();
        while (n < num) {
            while (j < right) {
                res.push_back(matrix[i][j]);
                j++;
                n++;
            }
            if (n >= num) return res;
            right--;
            j--;
            i++;
            while (i < down) {
                res.push_back(matrix[i][j]);
                i++;
                n++;
            }
            if (n >= num) return res;
            down--;
            i--;
            j--;
            while (j >= left) {
                res.push_back(matrix[i][j]);
                j--;
                n++;
            }
            if (n >= num) return res;
            left++;
            j++;
            i--;
            while (i >= up) {
                res.push_back(matrix[i][j]);
                i--;
                n++;
            }
            if (n >= num) return res;
            up++;
            i++;
            j++;
        }
        return res;
    }
};