力扣-剑指 Offer 32 - I. 从上到下打印二叉树（C++）- 层次遍历

女爷i 2022-09-09 06:18 75阅读 0赞

题目链接：[https://leetcode-cn.com/problems/cong-shang-dao-xia-da-yin-er-cha-shu-lcof/][https_leetcode-cn.com_problems_cong-shang-dao-xia-da-yin-er-cha-shu-lcof]  
题目如下：  
![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_17_color_FFFFFF_t_70_g_se_x_16]

/**
     * Definition for a binary tree node.
     * struct TreeNode {
     *     int val;
     *     TreeNode *left;
     *     TreeNode *right;
     *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
     * };
     */
    class Solution {
        
    public:
        vector<int> levelOrder(TreeNode* root) {
        
            //层次遍历，使用队列
            vector<int> result;
    
            if(root==NULL) return result;
    
            queue<TreeNode*> que;
            que.push(root);
    
            while(!que.empty()){
        
                int size=que.size();
    
                while(size--){
        //从第一层开始依次往下遍历
                    TreeNode* temp=que.front();
    
                    result.push_back(temp->val);
                    que.pop();
    
                    if(temp->left) que.push(temp->left);
                    if(temp->right) que.push(temp->right);
                }
            }
    
            return result; 
        }
    };

[https_leetcode-cn.com_problems_cong-shang-dao-xia-da-yin-er-cha-shu-lcof]: https://leetcode-cn.com/problems/cong-shang-dao-xia-da-yin-er-cha-shu-lcof/
[watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBASkluZ2xlczEyMw_size_17_color_FFFFFF_t_70_g_se_x_16]: /images/20220829/1d6634e98ab34821a5bb0a2a7e28440f.png