PTA 1110 Complete Binary Tree

题目描述

分析：判断所给树是否是完全二叉树，层序遍历二叉树，判断即可

#include<cstdio>
#include<queue>
#include<iostream>
#include<string>
#include<algorithm>
using namespace std;
struct Node{
    int left=-1,right=-1;
}tree[25];

int n;

bool child [25]={false};

bool layer(int root,int &last){
    queue<int> q;
    q.push(root);
    int num=0;
    while (!q.empty())
    {
        int top=q.front();
        q.pop();
        if(top!=-1){
            num++;
            last=top;
        }
        else{
            return num==n;
        }
        q.push(tree[top].left);
        q.push(tree[top].right);
    }
}

int main(){
    scanf("%d",&n);
    for(int i=0;i<n;i++){
        string x,y;
        cin>>x>>y;
        if(x!="-"){
            tree[i].left=stoi(x);
            child[stoi(x)]=true;
        }
        if(y!="-"){
            tree[i].right=stoi(y);
            child[stoi(y)]=true;
        }
    }
    int last=-1;
    int root=find(child,child+n,false)-child;
    bool flag=layer(root,last);
    if(flag)
    printf("YES %d\n",last);
    else{
        printf("NO %d\n",root);
    }
}