力扣-513题找树左下角的值（C++）- 层序

骑猪看日落 2022-09-17 03:09 197阅读 0赞

题目链接：[https://leetcode-cn.com/problems/find-bottom-left-tree-value/][https_leetcode-cn.com_problems_find-bottom-left-tree-value]  
题目如下：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16]  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16 1]

/**
     * 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) {
        
            if(root==NULL) return 0;
    
            queue<TreeNode*> que;
            que.push(root);
    
            int result=-1,flag;
    
            //层序遍历
            while(!que.empty()){
        
                int size=que.size();
                flag=1;
                //cout<<size<<endl;
                while(size--){
        //对每一层进行检索，注：需要后减一
                    TreeNode* temp=que.front();
                    que.pop();
                    if(flag==1) {
        result=temp->val;flag=0;}
    
                    if(temp->left) que.push(temp->left);
                    if(temp->right) que.push(temp->right);
                }
            }
    
            return result;
        }
    };

[https_leetcode-cn.com_problems_find-bottom-left-tree-value]: https://leetcode-cn.com/problems/find-bottom-left-tree-value/
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16]: /images/20220828/3cab88d6d1674d98aadb5e5c99a27c0d.png
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_20_color_FFFFFF_t_70_g_se_x_16 1]: /images/20220828/3b6794c3b276403ca25c0867bdacd5c3.png