POJ 2387 Til the Cows Come Home(最短路模板)

题目链接：http://poj.org/problem?id=2387

题意：有n个城市点，m条边，求n到1的最短路径。n<=1000; m<=2000

　　就是一个标准的最短路模板。

 #include<iostream>
 #include<algorithm>
 #include<cstring>
 #include<vector>
 #include<queue>

 using namespace std;
 const int maxn = ;
 const int INF = 0x3f3f3f3f3f;
 int n, m;
 struct node{
     int to, cost;
     node() {}
     node(int a, int b) :to(a), cost(b) {}
 };
 vector<node> e[maxn];
 int vis[maxn], f[maxn], dis[maxn];
 void SPFA(int s)
 {
     for (int i = ; i < maxn; i++) {
         vis[i] = ; f[i] = ;
         dis[i] = INF;
     }
     dis[s] = ;
     vis[s] = ; f[s]++;
     queue<int>Q;
     Q.push(s);
     while (!Q.empty()) {
         int t = Q.front(); Q.pop();
         vis[t] = ;
         for (int i = ; i < e[t].size(); i++) {
             int tmp = e[t][i].to;
             if (dis[tmp] > dis[t] + e[t][i].cost) {
                 dis[tmp] = dis[t] + e[t][i].cost;
                 if (!vis[tmp]) {
                     vis[tmp] = ;
                     Q.push(tmp);
                     if (++f[tmp] > n)return;
                 }
             }
         }
     }
     return;
 }
 int main()
 {
     ios::sync_with_stdio(false);
     while (cin >> m >> n) {
         for (int a, b, c, i = ; i <= m; i++) {
             cin >> a >> b >> c;
             e[a].push_back(node(b, c));
             e[b].push_back(node(a, c));
         }
         SPFA();
         cout << dis[n] << endl;
     }
     return ;
 }