-
Notifications
You must be signed in to change notification settings - Fork 3
Expand file tree
/
Copy pathLeetCode_00103.java
More file actions
62 lines (58 loc) · 1.89 KB
/
LeetCode_00103.java
File metadata and controls
62 lines (58 loc) · 1.89 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
package com.github.jerring.leetcode;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
public class LeetCode_00103 {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> res = new LinkedList<>();
Queue<TreeNode> queue = new LinkedList<>();
if (root != null) {
queue.offer(root);
}
// 从左往右标志
boolean leftToRight = true;
while (!queue.isEmpty()) {
int size = queue.size();
LinkedList<Integer> level = new LinkedList<>();
while (size-- != 0) {
TreeNode node = queue.poll();
if (leftToRight) {
level.addLast(node.val); // 从后面加
} else {
level.addFirst(node.val); // 从前面加
}
if (node.left != null) {
queue.offer(node.left);
}
if (node.right != null) {
queue.offer(node.right);
}
}
res.add(level);
// 每一层结束前反转标志
leftToRight = !leftToRight;
}
return res;
}
// public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
// List<List<Integer>> res = new ArrayList<>();
// traverse(root, 1, res);
// return res;
// }
//
// private void traverse(TreeNode root, int level, List<List<Integer>> res) {
// if (root == null) {
// return;
// }
// if (res.size() < level) {
// res.add(new ArrayList<>());
// }
// if ((level & 1) == 1) {
// res.get(level - 1).add(root.val);
// } else {
// res.get(level - 1).add(0, root.val);
// }
// traverse(root.left, level + 1, res);
// traverse(root.right, level + 1, res);
// }
}