LeetCode Spiral Matrix

题目：

Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order.

For example,
Given the following matrix:

[ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ]]

You should return [1,2,3,6,9,8,7,4,5].

class Solution {public:vector<int> spiralOrder(vector<vector<int> > &matrix) {if (matrix.size() == 0)return vector<int>();vector<int> ans;int m = matrix.size();int n = matrix[0].size();int x1 = 0, y1 = 0, x2 = m - 1, y2 = n - 1;while (x1 <= x2 && y1 <= y2) {for (int j = y1; j <= y2; j++)ans.push_back(matrix[x1][j]);for (int i = x1 + 1; i <= x2; i++)ans.push_back(matrix[i][y2]);if (x1 != x2) {for (int j = y2 - 1; j >= y1; j--)ans.push_back(matrix[x2][j]);}if (y1 != y2) {for (int i = x2 - 1; i >= x1 + 1; i--)ans.push_back(matrix[i][y1]);}x1++, y1++, x2--, y2--;}return ans;}};