二叉树层次遍历

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

void Print(const vector<int> &v)
{
    for(auto it:v)
    {
        cout<<it<<" ";
    }
    cout<<endl;
}
struct Treenode//定义树的节点 
{
    int val;
    Treenode* left;
    Treenode* right;
    Treenode(int _val):val(_val),left(nullptr),right(nullptr){}
};
//[in] 树的根节点
//[out] 一维vector的层次遍历结果 
//层次遍历关键在于queue的使用 
vector<int> cenci(Treenode* root)
{
    vector<int> result;
    queue<Treenode*> que;
    //if(root==nullptr) return nullptr;
    que.push(root);
    while(!que.empty())
    {
        Treenode* node=que.front();
        que.pop();
        if(node->left) que.push(node->left);
        if(node->right) que.push(node->right);
        result.push_back(node->val);
    }
    return result;
}
//[in]树的根节点 
//[out]二维vector的层次遍历结果 
vector<vector<int>> bianli(Treenode* root)
{
    vector<vector<int>> result;//返回结果 
    queue<Treenode*> que;
    que.push(root);
    
    while(!que.empty())
    {
        vector<int> v;
        size_t size=que.size();//当前行节点个数 
        for(size_t i=0;i<size;++i)//当前行节点的所有子节点加入队列 
        {
            Treenode* node=que.front();
            que.pop();
            if(node->left) que.push(node->left); 
            if(node->right) que.push(node->right);
            v.push_back(node->val);
        }
        result.push_back(v);
    }
    return result; 
    
}
int main(int argc, char *argv[])
{

    Treenode *t1=new Treenode(2);
    Treenode *t2=new Treenode(3);
    Treenode *t3=new Treenode(4);
    Treenode *t4=new Treenode(5);
    t1->left=t2;
    t1->right=t3;
    t2->left=t4;
    //vector<int> result= cenci(t1);
    //Print(result);
    vector<vector<int>> result=bianli(t1);
    for(auto it:result)//遍历输出结果 
    {
        for(auto it2:it)
        {
            cout<<it2<<" ";
        }
    }
    return 0;
}