uva 10801 SPFA

#include 
using namespace std;
typedef pairpii;
priority_queue, greater > q;
const int N = 105;
const int INF = 1E9;
int n, k, T[6], w[N][N], arr[N], d[N];
bool vis[N];

inline void read()
{
	for (int i = 0; i < N; i++)
	{
		w[i][i] = INF;
		for (int j = i + 1; j < N; j++)
			w[i][j] = w[j][i] = INF;
	}
	for (int i = 0; i < n; i++)
		cin >> T[i];
	char ch;
	for (int i = 0; i < n; i++)
	{
		int pos = 0;
		do
		{
			cin >> arr[pos++];
		}
		while (cin.get() != '\n');
		for (int j = 0; j < pos; j++)
			for (int k = j; k < pos; k++)
			{
				int tmp = abs(arr[j] - arr[k]) * T[i];
				if (tmp < w[arr[j]][arr[k]])
					w[arr[j]][arr[k]] = w[arr[k]][arr[j]] = tmp;
			}
	}
}

inline void SPFA(int src)
{
	memset(vis, 0, sizeof(vis));
	for (int i = 0; i < N; i++)
		d[i] = INF;
	d[src] = 0;
	queueq;
	q.push(src);
	while (!q.empty())
	{
		int u = q.front(); q.pop();
		vis[u] = false;
		for (int i = 0; i < N; i++)
			if (u == 0)
			{
				if (d[i] > d[u] + w[u][i])
				{
					d[i] = d[u] + w[u][i];
					if (!vis[i])
					{
						vis[i] = true;
						q.push(i);
					}
				}
			}
			else if (d[i] > d[u] + w[u][i] + 60)
			{
				d[i] = d[u] + w[u][i] + 60;
				if (!vis[i])
				{
					vis[i] = true;
					q.push(i);
				}
			}
	}
}

int main(int argc, char const *argv[])
{
	while (cin >> n >> k)
	{
		read();
		SPFA(0);
		if (d[k] != INF) cout << d[k] << endl;
		else cout << "IMPOSSIBLE" << endl;
	}
	return 0;
}

求最短路spfa

注意：起点需要特别考虑：起点不需要换成时间