LeetCode 513 Find Bottom Left Tree Value (BFS)

Given a binary tree, find the leftmost value in the last row of the tree.

Example 1:

Input:

2
/ \
1   3

Output:
1

Example 2: 

Input:

1
/ \
2   3
/   / \
4   5   6
/
7

Output:
7

Note: You may assume the tree (i.e., the given root node) is not NULL.

题目链接：https://leetcode.com/problems/find-bottom-left-tree-value/description/

题目分析：裸BFS，先右后左

/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int findBottomLeftValue(TreeNode root) {
Queue<TreeNode> q = new LinkedList<>();
q.add(root);
int ans = root.val;
while (!q.isEmpty()) {
TreeNode cur = q.poll();
ans = cur.val;
if (cur.right != null) {
q.add(cur.right);
}
if (cur.left != null) {
q.add(cur.left);
}
}
return ans;
}
}