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BinaryTreeZigzagLevelOrderTraversal.java
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BinaryTreeZigzagLevelOrderTraversal.java
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package com.leetcode;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
public class BinaryTreeZigzagLevelOrderTraversal {
//https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/
class Solution {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> result = new LinkedList<>();
if(root == null) return result;
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
boolean direction = false;
while(queue.size() > 0){
direction = !direction;
Queue<TreeNode> level = new LinkedList<>();
List<Integer> rlevel = new LinkedList<>();
while(queue.size() > 0){
TreeNode node = queue.poll();
if(direction){
rlevel.add(node.val);
}else{
rlevel.add(0,node.val);
}
if(node.left != null) level.add(node.left);
if(node.right != null) level.add(node.right);
}
result.add(rlevel);
queue = level;
}
return result;
}
}
//Definition for a binary tree node /
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode() {}
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
}