题目

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.

题目地址

讲解

这道题感觉挺简单的,首先我想到的是一定要选深度最大的节点,然后他要最左边的,那么我们可以先右后左的进行遍历,最后左边就可以覆盖右边了。

java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 result;
    private int maxDepth=0;
    public int findBottomLeftValue(TreeNode root) {
        inOrder(root, 0);
        return result;
    }
    
    private void inOrder(TreeNode root, int depth){
        if(root==null){
            return;
        }
        if(maxDepth<=depth){
            maxDepth=depth;
            result = root.val;
        }
        if(root.right!=null){
            inOrder(root.right, depth+1);
        }
        if(root.left!=null){
            inOrder(root.left, depth+1);
        }
    }
}

liuqinh2s
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