[leetcode] 102. Binary Tree Level Order Traversal

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Binary Tree Level Order Traversal

描述

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,null,null,15,7],

  3
 / \
9 20
    / \
   15 7

return its level order traversal as:

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

我的代码

简单的bfs。

/*** 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<vector<int>> levelOrder(TreeNode* root) {vector<vector<int>> rlt;queue<TreeNode*> q;if (root){q.push(root);while(q.size()!=0){vector<int> qTmp; //一定要注意要先创建一个vector，再往vector<vector<>>里面放int _siz=q.size();while(_siz){TreeNode* tmp = q.front();qTmp.push_back(tmp->val);if (tmp->left){q.push(tmp->left);}if (tmp->right){q.push(tmp->right);}q.pop();_siz--;}rlt.push_back(qTmp);}}return rlt;}
};

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