poj2449 k短路问题

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

using namespace std;
const int maxn = 1000 + 10;
int N, M;
int S, T, K;
struct edge { int v, c; };
vector<edge> G[maxn];           //正向边
vector<edge> P[maxn];           //反向边
int g[maxn];                    //求解出h函数的值
struct Dij
{
    int u, c;
    bool operator<(const Dij&r) const
    {
        return c>r.c;
    }
};
bool vis[maxn];
void dijkstra(int s)
{
    memset(g, 0x3f, sizeof(g));
    g[s] = 0;
    memset(vis, 0, sizeof(vis));
    priority_queue<Dij> que;
    que.push((Dij){s, 0});
    while(!que.empty())
    {
        Dij tp = que.top(); que.pop();
        int u=tp.u;
        if(vis[u]) continue;
        vis[u] = 1;
        for(int i=0; i<P[u].size(); i++)
        {
            int v = P[u][i].v, cost = P[u][i].c;
            if(g[v] > g[u]+cost)
            {
                g[v] = g[u]+cost;
                que.push((Dij){v, g[v]});
            }
        }
    }
}

struct Astar
{
    int h, g, u;
    bool operator< (const Astar& r) const
    {
        return h+g > r.h+r.g;
    }
};

int times[maxn];
int astar()
{
    memset(times, 0, sizeof(times));
    priority_queue<Astar> que;
    que.push((Astar){0, g[S], S});
    if(S == T) K++;
    while(!que.empty())
    {
        Astar tp = que.top(); que.pop();
        int u = tp.u;
        times[u]++;
        if(times[u]==K && u==T) return tp.h;
        else if(times[u] > K) continue;
        for(int i=0; i<G[u].size(); i++)
        {
            int v = G[u][i].v, c=G[u][i].c;
            que.push((Astar){tp.h+c, g[v], v});
        }
    }
    return -1;
}

int main()
{
    scanf("%d%d", &N, &M);
    for(int i=0; i<M; i++)
    {
        int u, v, t;
        scanf("%d%d%d", &u, &v, &t);
        G[u].push_back((edge){v, t});
        P[v].push_back((edge){u, t});
    }
    scanf("%d%d%d", &S, &T, &K);
    dijkstra(T);
    int res = astar();
    printf("%d\n", res);
    return 0;
}