[leetcode]Binary Tree Level Order Traversal-白红宇

[leetcode]Binary Tree Level Order Traversal

阅读量：5119 次

发布时间：2019-06-13

本文共 1199 字，大约阅读时间需要 3 分钟。

Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

For example:

Given binary tree {3,9,20,#,#,15,7},

3   / \  9  20    /  \   15   7

return its level order traversal as:

[  [3],  [9,20],  [15,7]]

confused what "{1,#,2,3}" means?

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    vector
    
     
       > levelOrder(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        vector
      
       
        > result;        if(!root) return result;                queue
        
          q1,q2;        q1.push(root);                TreeNode *cur;        vector
         
           tmp; while(!q1.empty()){ tmp.clear(); while(!q1.empty()){ cur = q1.front(); q1.pop(); tmp.push_back(cur -> val); if(cur -> left) q2.push(cur -> left); if(cur -> right) q2.push(cur -> right); } result.push_back(tmp); swap(q1, q2); } return result; }};