POJ 2367 Genealogical tree 拓撲排序

POJ 2367 Genealogical tree 拓撲排序

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

5
0
4 5 1 0
1 0
5 3 0
3 0

Sample Output

2 4 5 3 1

Source

Ural State University Internal Contest October'2000 Junior Session

一個標准的拓撲排序題解。

要點：

1 查找沒有父親節點的點，先輸出這些點

2 使用一個數組，del[i]記錄已經輸出的點

3 輸出了的點不再計算在父親節點中，循環第1步，直到輸出所有點

#include 
#include 
#include 
using namespace std;

const int MAX_N = 101;
vector pars[MAX_N];
bool del[MAX_N];

void topologicalPrint(int n)
{
	int c = 0;
	while (c < n)
	{
		for (int i = 1; i <= n; i++)
		{
			if (del[i]) continue;//注意：已經刪除點直接跳過

			int ps = 0;
			for (int j = 0; j < (int)pars[i].size() && !ps; j++)
			{
				if (!del[pars[i][j]]) ps++;
			}
			if (!ps)
			{
				del[i] = true;//刪除該點
				printf("%d ", i);
				c++;
			}
		}
	}
}

int main()
{
	int N, v;
	while (~scanf("%d", &N))
	{
		for (int i = 1; i <= N; i++)
		{
			pars[i].clear();
			del[i] = false;
		}
		for (int i = 1; i <= N; i++)
		{
			scanf("%d", &v);
			while (v)
			{
				pars[v].push_back(i);
				scanf("%d", &v);
			}
		}
		topologicalPrint(N);
		putchar('\n');
	}
	return 0;
}