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P54.java
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P54.java
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/*
54. 螺旋矩阵
https://leetcode-cn.com/problems/spiral-matrix/
https://leetcode-cn.com/explore/interview/card/top-interview-questions-hard/55/array-and-strings/124/
给定一个包含 m x n 个元素的矩阵(m 行, n 列),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:
[
[ 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:
[
[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]
*/
import java.util.*;
public class P54 {
public static void main(String[] args) {
int[][] nums = new int[][] {
{ 1, 2, 3, 4 },
{ 5, 6, 7, 8 },
{ 9, 10, 11, 12 }
};
System.out.println(new Solution().spiralOrder(nums));
}
static class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
List<Integer> results = new ArrayList<>();
if (matrix == null || matrix.length == 0) {
return results;
}
int[] dx = { 0, 1, 0, -1 };
int[] dy = { 1, 0, -1, 0 };
int x = 0;
int y = 0;
int dir = 0;
for (int i = 0; i < matrix.length * matrix[0].length; i++) {
results.add(matrix[x][y]);
matrix[x][y] = 0;
int next_x = x + dx[dir];
int next_y = y + dy[dir];
if (next_x < 0 || next_x >= matrix.length
|| next_y < 0 || next_y >= matrix[0].length
|| matrix[next_x][next_y] == 0) {
dir = (dir + 1) % 4;
next_x = x + dx[dir];
next_y = y + dy[dir];
}
x = next_x;
y = next_y;
}
return results;
}
}
}