共计 722 个字符，预计需要花费 2 分钟才能阅读完成。
Given a binary tree, find the leftmost value in the last row of the tree.
Example 1:Input:
2
/ \ 1 3
Output:1Example 2: Input:
1
/ \
2 3
/ / \
4 5 6
/
7
Output: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;
}
}
