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BinaryTreeLevelOrderTraversalII.java
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BinaryTreeLevelOrderTraversalII.java
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package com.leetcode;
import java.util.LinkedList;
import java.util.List;
import java.util.Queue;
public class BinaryTreeLevelOrderTraversalII {
//https://leetcode.com/problems/binary-tree-level-order-traversal-ii/
class Solution {
public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result = new LinkedList<>();
if(root == null) return result;
Queue<TreeNode> queue = new LinkedList<>();
queue.offer(root);
while(queue.size() > 0){
LinkedList<TreeNode> level = new LinkedList<>();
List<Integer> values = new LinkedList<>();
while(queue.size() > 0){
TreeNode node = queue.poll();
values.add(node.val);
if(node.left != null)
level.offer(node.left);
if(node.right != null)
level.offer(node.right);
}
result.add(0,values);
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;
}
}
}