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leetcode103.java
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leetcode103.java
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/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> result = new ArrayList<>();
zigzagTraverse(root,result,0);
return result;
}
private void zigzagTraverse(TreeNode root, List<List<Integer>> res, int level){
if(root == null)
return;
if(res.size() <= level){
res.add(new LinkedList<Integer>());
}
List<Integer> curLevel = res.get(level);
if(level % 2 == 0)
curLevel.add(root.val);
else
curLevel.add(0,root.val);
zigzagTraverse(root.left,res,level+1);
zigzagTraverse(root.right,res,level+1);
}
}