LeetCode513. Find Bottom Left Tree Value

Find Bottom Left Tree Value"/>

LeetCode513. Find Bottom Left Tree Value

文章目录

• • 一、题目
  • 二、题解

一、题目

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

Example 1:

Input: root = [2,1,3]
Output: 1
Example 2:

Input: root = [1,2,3,4,null,5,6,null,null,7]
Output: 7

Constraints:

The number of nodes in the tree is in the range [1, 104].
-231 <= Node.val <= 231 - 1

二、题解

层序遍历法

/*** Definition for a binary tree node.* struct TreeNode {*     int val;*     TreeNode *left;*     TreeNode *right;*     TreeNode() : val(0), left(nullptr), right(nullptr) {}*     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}*     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}* };*/
class Solution {
public:int findBottomLeftValue(TreeNode* root) {int res = 0;queue<TreeNode*> q;q.push(root);while(!q.empty()){int size = q.size();int iniSize = size;while(size--){TreeNode* t = q.front();q.pop();if(size == iniSize - 1) res = t->val;if(t->left) q.push(t->left);if(t->right) q.push(t->right);}}return res;}
};