poj 1125 Stockbroker Grapevine dijkstra算法实现最短路径

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Stockbroker Grapevine

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 23760		Accepted: 13050

Description

Stockbrokers are known to overreact to rumours. You have been contracted to develop a method of spreading disinformation amongst the stockbrokers to give your employer the tactical edge in the stock market. For maximum effect, you have to spread the rumours
in the fastest possible way. 



Unfortunately for you, stockbrokers only trust information coming from their "Trusted sources" This means you have to take into account the structure of their contacts when starting a rumour. It takes a certain amount of time for a specific stockbroker to pass
the rumour on to each of his colleagues. Your task will be to write a program that tells you which stockbroker to choose as your starting point for the rumour, as well as the time it will take for the rumour to spread throughout the stockbroker community.
This duration is measured as the time needed for the last person to receive the information.

Input

Your program will input data for different sets of stockbrokers. Each set starts with a line with the number of stockbrokers. Following this is a line for each stockbroker which contains the number of people who they have contact with, who these people are,
and the time taken for them to pass the message to each person. The format of each stockbroker line is as follows: The line starts with the number of contacts (n), followed by n pairs of integers, one pair for each contact. Each pair lists first a number referring
to the contact (e.g. a '1' means person number one in the set), followed by the time in minutes taken to pass a message to that person. There are no special punctuation symbols or spacing rules. 



Each person is numbered 1 through to the number of stockbrokers. The time taken to pass the message on will be between 1 and 10 minutes (inclusive), and the number of contacts will range between 0 and one less than the number of stockbrokers. The number of
stockbrokers will range from 1 to 100. The input is terminated by a set of stockbrokers containing 0 (zero) people. 

Output

For each set of data, your program must output a single line containing the person who results in the fastest message transmission, and how long before the last person will receive any given message after you give it to this person, measured in integer minutes. 

It is possible that your program will receive a network of connections that excludes some persons, i.e. some people may be unreachable. If your program detects such a broken network, simply output the message "disjoint". Note that the time taken to pass the
message from person A to person B is not necessarily the same as the time taken to pass it from B to A, if such transmission is possible at all.

Sample Input

3
2 2 4 3 5
2 1 2 3 6
2 1 2 2 2
5
3 4 4 2 8 5 3
1 5 8
4 1 6 4 10 2 7 5 2
0
2 2 5 1 5
0

Sample Output

3 2
3 10

题目大意是信息必须通过关系网传播，信息在人与人之间传播需要一定的时间，现在给定一个关系网络，让我们求从哪个点开始传播才能使传播给所有人所有的时间最短，需要注意的是，信息的传播可以同时进行。

这题使用的dijkstra算法的优先级队列实现方式，

#include<stdio.h>
#include<queue>
#include<utility>
#include<string.h>
#define N 110
using namespace std;
int map[N][N];
int m;
int dij(int i)
{
	int count = 0;//¼Ç¼ËÑË÷¹ýµÄµã£¬ÓÃÀ´ÅжÏÊÇ·ñÁªÍ¨
	int ans = 0;
	priority_queue<pair<int, int> , vector<pair<int, int> > , greater<pair<int, int > > > pq;
	bool used[N] = {0};
	pair<int ,int > pa;
	pa.first = 0;
	pa.second = i;
	pq.push(pa);
	while(!pq.empty())
	{
		pa = pq.top();
		pq.pop();
		if(used[pa.second])
			continue;
		used[pa.second] = 1;
		count ++;
		ans = ans > pa.first ? ans : pa.first;
		if(count == m)
			break;
		int j;
		for(j = 1; j <= m; j++)
		{
			if(map[pa.second][j] && !used[j])
			{
				pair<int, int> new_p;
				new_p.first = pa.first + map[pa.second][j];
				new_p.second = j;
				pq.push(new_p);
			}
		}
	}
	if(count == m)
		return ans;
	else
		return 0x7fffffff;
}
int main()
{
//	freopen("in.txt", "r", stdin);
	int n;
	while(scanf("%d", &m), m)
	{
		memset(map, 0, sizeof(map));
		int j;
		int i;
		int min = 0x7fffffff, mark;
		for(j = 1; j <= m; j++)
		{
			scanf("%d", &n);
			for(i = 1; i <= n; i++)
			{
				int to, time;
				scanf("%d%d",&to, &time);
				map[j][to] = time;
			}
		}
		for(i = 1; i <= m; i++)
		{
			int temp = dij(i);
			if(temp < min)
			{
				min = temp;
				mark = i;
			}
		}
		if(min == 0x7fffffff)
			printf("disjoint\n");
		else
			printf("%d %d\n", mark, min);
	}
	return 0;
}