LeetCode Binary Tree Level Order Traversal

题目

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]]

 

层序遍历，bfs即可

 

代码：

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {struct pt//bfs探测用点{TreeNode *node;//探测到的位置int level;//相应的层pt(TreeNode *n=NULL,int l=0):node(n),level(l){}};public:    vector<vector<int> > levelOrder(TreeNode *root) {        vector<vector<int>> ret;//返回值deque<pt> queue(1,pt(root));//bfs队列while(!queue.empty())//bfs{if(queue.front().node!=NULL){if(queue.front().level>=ret.size())ret.push_back(vector<int>());ret[queue.front().level].push_back(queue.front().node->val);queue.push_back(pt(queue.front().node->left,queue.front().level+1));queue.push_back(pt(queue.front().node->right,queue.front().level+1));}queue.pop_front();}return ret;    }};