poj 2367 Genealogical tree（topsort）

最新推荐文章于 2019-02-15 21:50:59 发布

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本文探讨了火星上混乱的血缘关系系统，并提出了一个程序解决方案，用于确保议会成员发言顺序早于其后代。

Language:

Genealogical tree

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 3063		Accepted: 2072		Special Judge

Description

The system of Martians' blood relations is confusing enough. Actually, Martians bud when they want and where they want. They gather together in different groups, so that a Martian can have one parent as well as ten. Nobody will be surprised by a hundred of children. Martians have got used to this and their style of life seems to them natural.
And in the Planetary Council the confusing genealogical system leads to some embarrassment. There meet the worthiest of Martians, and therefore in order to offend nobody in all of the discussions it is used first to give the floor to the old Martians, than to the younger ones and only than to the most young childless assessors. However, the maintenance of this order really is not a trivial task. Not always Martian knows all of his parents (and there's nothing to tell about his grandparents!). But if by a mistake first speak a grandson and only than his young appearing great-grandfather, this is a real scandal.
Your task is to write a program, which would define once and for all, an order that would guarantee that every member of the Council takes the floor earlier than each of his descendants.

Input

The first line of the standard input contains an only number N, 1 <= N <= 100 — a number of members of the Martian Planetary Council. According to the centuries-old tradition members of the Council are enumerated with the natural numbers from 1 up to N. Further, there are exactly N lines, moreover, the I-th line contains a list of I-th member's children. The list of children is a sequence of serial numbers of children in a arbitrary order separated by spaces. The list of children may be empty. The list (even if it is empty) ends with 0.

Output

The standard output should contain in its only line a sequence of speakers' numbers, separated by spaces. If several sequences satisfy the conditions of the problem, you are to write to the standard output any of them. At least one such sequence always exists.

Sample Input

Sample Output

2 4 5 3 1

Source

Ural State University Internal Contest October'2000 Junior Session

直接的topsort，有两种做法，一种dfs ，一种用数据结构的方法

dfs代码：

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
#include<vector>
using namespace std;

#define N 105
int a[N][N];
int vis[N],ans[N];
int n,m;

int dfs(int x)
{
	vis[x]=-1;
	int i;
	for(i=1;i<=n;i++)
	  if(a[x][i])
	  {
	  	if(vis[i]==-1)
			return 0;
		else
			if(!vis[i]&&!dfs(i))
			return 0;
	  }

	 vis[x]=1;
     ans[--m]=x;
     return 1;
}

void print()
{
	int i;
	for(i=0;i<n-1;i++)
		printf("%d ",ans[i]) ;
	printf("%d\n",ans[n-1]);
}

int main()
{
	int i,j,x;
	while(~scanf("%d",&n))
	{
		memset(vis,0,sizeof(vis));
		memset(a,0,sizeof(a));
		for(i=1;i<=n;i++)
		{
			while(1)
			{
				scanf("%d",&x);
				if(!x) break;
				a[i][x]=1;
			}
		}
          m=n;
         for(i=1;i<=n;i++)
			if(vis[i]==0)
			   if(!dfs(i))
			    break;
		print();
	}

   return 0;
}

数据结构代码：

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<queue>
#include<stack>
using namespace std;

#define N 105

int a[N][N];
int vis[N],ans[N];
int n,m;

int dfs(int x)
{
	vis[x]=-1;
	int i;
	for(i=1;i<=n;i++)
	  if(a[x][i])
	  {
	  	if(vis[i]==-1)
			return 0;
		else
			if(!vis[i]&&!dfs(i))
			return 0;
	  }

	 vis[x]=1;
     ans[--m]=x;
     return 1;
}

void print()
{
	int i;
	for(i=0;i<n-1;i++)
		printf("%d ",ans[i]) ;
	printf("%d\n",ans[n-1]);
}

int main()
{
	int i,j,x;
	while(~scanf("%d",&n))
	{
		memset(vis,0,sizeof(vis));
		memset(a,0,sizeof(a));
		for(i=1;i<=n;i++)
		{
			while(1)
			{
				scanf("%d",&x);
				if(!x) break;
				a[i][x]=1;
			}
		}
          m=n;
         for(i=1;i<=n;i++)
			if(vis[i]==0)
			   if(!dfs(i))
			    break;
		print();
	}

   return 0;
}