POJ 3635（HDU 1676）Full Tank?

题目：http://poj.org/problem?id=3635

用优先级队列+dijkstra

//#include<bits/stdc++.h>
//#define DEBUG
#include<cstdio>
#include<iostream>
#include<cstring>
#include<string>
#include<queue>
#include<map>
#include<vector>
#include<set>
#include<cmath>
#include<cstdlib>
#include<algorithm>
#include<stack>

using namespace std;

typedef long long ll;
typedef unsigned int ui;
const int maxn = 1005;
const ll mod = 1e9 + 7;
const double pi = acos(-1);

int n, m, cap, s, t, ans;
int a[maxn];
struct P
{
    int to, next, c;
}edge[maxn * 20];
int head[maxn], cnt;

inline void add(int u, int v, int c)
{
    edge[cnt].to = v;
    edge[cnt].c = c;
    edge[cnt].next = head[u];
    head[u] = cnt++;
}

struct node
{
    int v, oi, cost;
    bool operator>(node A) const
    {
        return cost > A.cost;
    }
};

bool vis[maxn][maxn];
int dis[maxn][maxn];

void BFS()
{
    memset(vis, 0, sizeof(vis));
    memset(dis, 0x3f, sizeof(dis));
    dis[s][0] = 0;
    priority_queue<node, vector<node>, greater<node> > PQ;

    PQ.push({s, 0, 0});
    while(!PQ.empty())
    {
        node cur = PQ.top();
        PQ.pop();
        if(vis[cur.v][cur.oi]) continue;
        vis[cur.v][cur.oi] = 1;
        if(cur.v == t)
        {
            cout << cur.cost << endl;
            return;
        }
        int u = cur.v;
        if(cur.oi + 1 <= cap && !vis[u][cur.oi + 1] && dis[u][cur.oi + 1] > dis[u][cur.oi] + a[u])
        {
            dis[u][cur.oi + 1] =  dis[u][cur.oi] + a[u];
            PQ.push({u, cur.oi + 1, cur.cost + a[u]});
        }
        for(int i = head[u]; ~i; i = edge[i].next)
        {
            int v = edge[i].to;
            int d = edge[i].c;
            if(cur.oi >= d && !vis[v][cur.oi - d] && dis[v][cur.oi - d] > cur.cost)
            {
                dis[v][cur.oi - d] = cur.cost;
                PQ.push({v, cur.oi - d, cur.cost});
            }
        }
    }
    cout << "impossible" << endl;
}

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    while(cin >> n >> m)
    {
        memset(head, -1, sizeof(head));
        cnt = 0;
        int u, v, c;
        for(int i = 0; i < n; i++)
            cin >> a[i];
        while(m--)
        {
            cin >> u >> v >> c;
            add(u, v, c);
            add(v, u, c);
        }
        int q;
        cin >> q;
        while(q--)
        {
            cin >> cap >> s >> t;
            BFS();
        }
    }
}