Leetcode 细节实现题 Spiral Matrix

Spiral Matrix

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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].

题意：以螺旋顺序输入矩阵中的数值
思路：
从左到右，从上到下，从右到左，从下到上按顺序遍历
将矩阵的(0,0)元素看成坐标原点，向右为x轴正方向，向下为y轴正方向
用四个变量，即两个坐标(startx, starty), (endx, endy) 表示每轮遍历的矩阵的左上角和右下角的坐标
复杂度：时间O(n^2)

vector<int> spiralOrder(vector<vector<int> > &matrix){vector<int> res;if(matrix.empty()) return res;int startx = 0, endx = matrix[0].size() - 1;int starty = 0, endy = matrix.size() - 1;while(startx <= endx && starty <= endy){for(int j = startx; j <= endx; ++j) res.push_back(matrix[starty][j]);starty++;for(int i = starty; i <= endy; ++i) res.push_back(matrix[i][endx ]);endx--;if(starty <= endy){for(int j = endx; j >= startx ; --j) res.push_back(matrix[endy ][j]);endy--;}if(startx <= endx){for(int i = endy; i >= starty; --i) res.push_back(matrix[i][startx]);startx++;}}return res;}