LeetCode 513 Find Bottom Left Tree Value (BFS)

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本文介绍了一种解决LeetCode上特定问题的方法：寻找二叉树最底层最左边的节点值。通过使用从右到左的广度优先搜索(BFS)，可以有效地找到目标节点。

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:

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;
    }
}