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 = 2010;
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 = 0; i < maxn; i++) {
        vis[i] = 0; f[i] = 0;
        dis[i] = INF;
    }
    dis[s] = 0;
    vis[s] = 1; f[s]++;
    queue<int>Q;
    Q.push(s);
    while (!Q.empty()) {
        int t = Q.front(); Q.pop();
        vis[t] = 0;
        for (int i = 0; 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] = 1;
                    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 = 1; i <= m; i++) {
            cin >> a >> b >> c;
            e[a].push_back(node(b, c));
            e[b].push_back(node(a, c));
        }
        SPFA(1);
        cout << dis[n] << endl;
    }
    return 0;
}