513. Find Bottom Left Tree Value

Given a binary tree, find the leftmost value in the last row of the tree.Example 1:Input:2/ \ 1 3Output:1Example 2: Input: 1 / \ 2 3 / / \4 5 6 / 7Output:7Note: You may assume the tree (i.e., the given root node) is not NULL.难度：medium题目：给定二叉树，找出其最左边的结点。注意：你可以认为树一定不为ＮＵＬＬ思路：ＢＦＳ， 层次遍历（先入右子树，再入左子树）。Runtime: 4 ms, faster than 71.59% of Java online submissions for Find Bottom Left Tree Value./** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */class Solution { public int findBottomLeftValue(TreeNode root) { Queue<TreeNode> queue = new LinkedList<>(); queue.add(root); TreeNode node = root; while (!queue.isEmpty()) { node = queue.poll(); if (node.right != null) { queue.add(node.right); } if (node.left != null) { queue.add(node.left); } } return node.val; }}