leetcode原地址：https://leetcode.cn/problems/spiral-matrix/description
描述
给你一个 m 行 n 列的矩阵 matrix ，请按照 顺时针螺旋顺序 ，返回矩阵中的所有元素。
示例 1：
输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
输出：[1,2,3,6,9,8,7,4,5]
示例 2：
输入：matrix = [[1,2,3,4],[5,6,7,8],[9,10,11,12]]
输出：[1,2,3,4,8,12,11,10,9,5,6,7]
提示：
m == matrix.length
n == matrix[i].length
1 <= m, n <= 10
-100 <= matrix[i][j] <= 100
题解
public List<Integer> spiralOrder(int[][] matrix) {List<Integer> res = new ArrayList<>();if (matrix == null || matrix.length == 0 || matrix[0].length == 0) {return res;}int top = 0;int left = 0;int right = matrix[0].length-1;int bottom = matrix.length-1;int cur = 0;while (right>left && bottom >top){//从左往右for(int i =left;i<right;i++){res.add(matrix[top][i]);}//从上到下for(int i =top;i<bottom;i++){res.add(matrix[i][right]);}//从右往左for(int i =right;i>left;i--){res.add(matrix[bottom][i]);}//从下到上for(int i =bottom;i>top;i--){res.add(matrix[i][left]);}left++;bottom--;top++;right--;}if (top == bottom) {for (int i = left; i <= right; i++) {res.add(matrix[top][i]);}} else if (left == right) {for (int i = top; i <= bottom; i++) {res.add(matrix[i][left]);}}return res;}
