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8 | 8 | import java.util.List;
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9 | 9 | import java.util.Queue;
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10 | 10 |
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11 |
| - |
12 | 11 | /**
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13 |
| - * 103. Binary Tree Zigzag Level Order Traversal |
14 |
| - * |
| 12 | + * 103. Binary Tree Zigzag Level Order Traversal |
| 13 | + * |
15 | 14 | Given a binary tree, return the zigzag level order traversal of its nodes' values.
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16 | 15 | (ie, from left to right, then right to left for the next level and alternate between).
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17 | 16 |
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30 | 29 | ]
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31 | 30 | */
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32 | 31 | public class _103 {
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33 |
| - public List<List<Integer>> zigzagLevelOrder(TreeNode root) { |
34 |
| - Queue<TreeNode> q = new LinkedList(); |
35 |
| - List<List<Integer>> levels = new ArrayList(); |
36 |
| - if (root == null) { |
37 |
| - return levels; |
38 |
| - } |
39 |
| - q.offer(root); |
40 |
| - boolean forward = true; |
41 |
| - while (!q.isEmpty()) { |
42 |
| - int size = q.size(); |
43 |
| - List<Integer> level = new ArrayList(); |
44 |
| - for (int i = 0; i < size; i++) { |
45 |
| - TreeNode curr = q.poll(); |
46 |
| - level.add(curr.val); |
47 |
| - if (curr.left != null) { |
48 |
| - q.offer(curr.left); |
| 32 | + public static class Solution1 { |
| 33 | + public List<List<Integer>> zigzagLevelOrder(TreeNode root) { |
| 34 | + Queue<TreeNode> q = new LinkedList(); |
| 35 | + List<List<Integer>> levels = new ArrayList(); |
| 36 | + if (root == null) { |
| 37 | + return levels; |
| 38 | + } |
| 39 | + q.offer(root); |
| 40 | + boolean forward = true; |
| 41 | + while (!q.isEmpty()) { |
| 42 | + int size = q.size(); |
| 43 | + List<Integer> level = new ArrayList(); |
| 44 | + for (int i = 0; i < size; i++) { |
| 45 | + TreeNode curr = q.poll(); |
| 46 | + level.add(curr.val); |
| 47 | + if (curr.left != null) { |
| 48 | + q.offer(curr.left); |
| 49 | + } |
| 50 | + if (curr.right != null) { |
| 51 | + q.offer(curr.right); |
| 52 | + } |
49 | 53 | }
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50 |
| - if (curr.right != null) { |
51 |
| - q.offer(curr.right); |
| 54 | + if (forward) { |
| 55 | + forward = false; |
| 56 | + levels.add(level); |
| 57 | + } else { |
| 58 | + Collections.reverse(level); |
| 59 | + levels.add(level); |
| 60 | + forward = true; |
52 | 61 | }
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53 | 62 | }
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54 |
| - if (forward) { |
55 |
| - forward = false; |
56 |
| - levels.add(level); |
57 |
| - } else { |
58 |
| - Collections.reverse(level); |
59 |
| - levels.add(level); |
60 |
| - forward = true; |
61 |
| - } |
| 63 | + return levels; |
62 | 64 | }
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63 |
| - return levels; |
64 | 65 | }
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65 | 66 | }
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