题目连接：Leetcode 054 Spiral Matrix
解题思路：维护一个矩阵标记每个位置是否走过，然后从0,0 的位置开始移动，向右，向下，向左，向上，每次到不能移动方向时，改变方向。
class Solution { public: vector<int> spiralOrder(vector<vector<int>>& matrix) { vector<int> ans; int m = matrix.size(); if (m == 0) return ans; int n = matrix[0].size(); if (n == 0) return ans; vector<bool> tmp; vector<vector<bool>> gph; for (int i = 0; i < n; i++) tmp.push_back(false); for (int i = 0; i < m; i++) gph.push_back(tmp); int d_x[4] = {0, 1, 0, -1}; int d_y[4] = {1, 0, -1, 0}; int d = 0, x = 0, y = 0, k = m * n; while (k--) { ans.push_back(matrix[x][y]); gph[x][y] = true; int xx = x + d_x[d], yy = y + d_y[d]; while (k && (xx<0 || xx>=m || yy<0 || yy>=n || gph[xx][yy])) { d = (d + 1) % 4; xx = x + d_x[d]; yy = y + d_y[d]; } x = xx, y = yy; } return ans; } };