LeetCode 54 Spiral Matrix (模拟 蛇形填数)

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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].

题目链接：https://leetcode.com/problems/spiral-matrix/

题目分析：模拟填数过程即可

public class Solution {public List<Integer> spiralOrder(int[][] matrix) {List<Integer> ans = new ArrayList<>();int n = matrix.length;if (n == 0) {return ans;}int m = matrix[0].length;int all = n * m, cnt = 0, i = 0, j = 0;boolean[][] vis = new boolean[n + 1][m + 1];while (cnt < all) {while (j < m && !vis[i][j]) {vis[i][j] = true;cnt ++;ans.add(matrix[i][j ++]);}j --;i ++;while (i < n && !vis[i][j]) {vis[i][j] = true;cnt ++;ans.add(matrix[i ++][j]);}i --;j --;while (j >= 0 && !vis[i][j]) {vis[i][j] = true;cnt ++;ans.add(matrix[i][j --]);}j ++;i --;while (i >= 0 && !vis[i][j]) {vis[i][j] = true;cnt ++;ans.add(matrix[i --][j]);}i ++;j ++;}return ans;}
}

其实不开boolean数组也可以

public class Solution {public List<Integer> spiralOrder(int[][] matrix) {List<Integer> ans = new ArrayList<>();int n = matrix.length;if (n == 0) {return ans;}int m = matrix[0].length;int left = 0, right = m - 1, down = n - 1, up = 0;while (true) {for (int j = left; j <= right; j ++) {ans.add(matrix[up][j]);}up ++;if (left > right || up > down) {break;}for (int i = up; i <= down; i ++) {ans.add(matrix[i][right]);}right --;if (left > right || up > down) {break;}for (int j = right; j >= left; j --) {ans.add(matrix[down][j]);}down --;if (left > right || up > down) {break;}for (int i = down; i >= up; i --) {ans.add(matrix[i][left]);}left ++;if (left > right || up > down) {break;}}return ans;}
}

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