Leetcode 513. Find Bottom Left Tree Value

题目链接

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

题目描述

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.

题解

递归遍历每一个节点，同时记录一下当前的深度，只有深度大于当前最大深度的时候，才更新值，不然节点遍历。

代码

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    private int value = 0;
    private int ant = Integer.MIN_VALUE;
    public int findBottomLeftValue(TreeNode root) {
        findBottomLeftValue(root, 0);
        return value;
    }
    
    public void findBottomLeftValue(TreeNode root, int level) {
        if (root == null) { return ; }
        findBottomLeftValue(root.left, level + 1);
        findBottomLeftValue(root.right, level + 1);
        if (level > ant) {
            ant = level;
            value = root.val;
        }
    }
}