1110 Complete Binary Tree——PAT甲级(测试点234)

Given a tree, you are supposed to tell if it is a complete binary tree.

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤20) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N−1. Then N lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a - will be put at the position. Any pair of children are separated by a space.

Output Specification:

For each case, print in one line YES and the index of the last node if the tree is a complete binary tree, or NO and the index of the root if not. There must be exactly one space separating the word and the number.

Sample Input 1:

9
7 8
- -
- -
- -
0 1
2 3
4 5
- -
- -

Sample Output 1:

YES 8

Sample Input 2:

8
- -
4 5
0 6
- -
2 3
- 7
- -
- -

Sample Output 2:

NO 1

 solution:
 

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
#define endl '\n'
const int maxn=50;
int l[maxn]={0},r[maxn]={0};
int vis[maxn]={0};
int main()
{
	int n;cin>>n;
	int num=0;
	memset(l,-1,sizeof l);
	memset(r,-1,sizeof r);
	for(int i=0;i<n;i++)
	{
		string a,b;cin>>a>>b;
		/*
		if(a!="-")l[i]=a-'0',vis[l[i]]=1,num++;
		if(b!="-")r[i]=b-'0',vis[r[i]]=1,num++;
		*/
		if(a.size()==1)//测试点234
		{
			if(a!="-")l[i]=a[0]-'0',vis[l[i]]=1,num++;
		}
		else if(a.size()==2)
		{
			if(a!="-")
			{
				l[i]=(a[0]-'0')*10+a[1]-'0';
				vis[l[i]]=1,num++;
			}
		}
		if(b.size()==1)
		{
			if(b!="-")r[i]=b[0]-'0',vis[r[i]]=1,num++;
		}
		else if(b.size()==2)
		{
			if(b!="-")
			{
				r[i]=(b[0]-'0')*10+b[1]-'0';
				vis[r[i]]=1,num++;
			}
		}
	}
	int head=0;
	while(vis[head])head++;
	queue<int>q;
	q.push(head);
	int tmp=1;
	int last=head;
	while(!q.empty())
	{
		if(l[q.front()]!=-1)q.push(l[q.front()]),tmp++,last=l[q.front()];
		else if(l[q.front()]==-1)
		{
			break;
		}
		if(r[q.front()]!=-1)q.push(r[q.front()]),tmp++,last=r[q.front()];
		else if(r[q.front()]==-1)
		{
			break;
		}
		q.pop();
	}
	if(tmp!=n)
	{
		cout<<"NO"<<' '<<head<<endl; 
	}
	else cout<<"YES"<<' '<<last<<endl;
}

 注意测试点234，可能为10位数