PAT (Advanced Level) Practice 1115 Counting Nodes in a BST

1、建二叉排序樹

2、層序遍歷，我是把每層的節點數記錄下來，最後輸出倒數兩個

ps：當n=1時，輸出“1 + 0 = 1” 

#include <iostream>
#include <vector>
#include <queue>
using namespace std;
struct node{
    node* lchild;
    node* rchild;
    int data,layer;
};
void insertNode(int n,node* &root){
    if(root==NULL){
        root = new node;
        root->lchild=NULL;
        root->rchild=NULL;
        root->data=n;
        return;
    }
    if(n<=root->data){
        insertNode(n,root->lchild);
    }else{
        insertNode(n,root->rchild);
    }
}

vector<int> v;
void layerTravel(node* root){
    int layer=0,num=0;
    queue<node*> q;
    root->layer=layer;
    q.push(root);
    while(!q.empty()){
        node* Node = q.front();
        q.pop();
        if(Node->lchild!=NULL){
            Node->lchild->layer=Node->layer+1;
            q.push(Node->lchild);
        }
        if(Node->rchild!=NULL){
            Node->rchild->layer=Node->layer+1;
            q.push(Node->rchild);
        }
        if(Node->layer!=layer){
            v.push_back(num);
            num=0;
            layer=Node->layer;
        }
        num++;
    }
    v.push_back(num);
}
int main()
{
    int n;
    cin>>n;
    node* root=NULL;
    for(int i=0;i<n;i++){
        int m;
        cin>>m;
        insertNode(m,root);
    }
    layerTravel(root);
    if(v.size()>=2){
        cout<<v[v.size()-1]<<" + "<<v[v.size()-2]<<" = "<<v[v.size()-1]+v[v.size()-2];
    }else{
        cout<<"1 + 0 = 1";
    }
    return 0;
}