POJ 2449

#include<queue>
#include<cstdio>
#include<string>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAXN = 1010;
const int MAXM = 100010;
const int INF = 0x7fffffff;
typedef struct{
    int to, next, w;
}Edge;
typedef struct Node{
    int p, g, h;
    Node(int p, int g, int h){
        this->p = p;
        this->g = g;
        this->h = h;
    }
    bool operator < (const Node &node) const{
        return node.g+node.h < g+h;
    }
}Node;
Edge edge[MAXM << 1];
int n, m;
int head[MAXN], tail[MAXN], dist[MAXN];
int cnt[MAXN], vis[MAXN];
void addEdge(int u, int v, int w, int k){
    edge[k].to = v;
    edge[k].w = w;
    edge[k].next = head[u];
    head[u] = k++;
    edge[k].to = u;
    edge[k].w = w;
    edge[k].next = tail[v];
    tail[v] = k;
}
void init(int s){
    memset(vis, 0, sizeof(vis));
    memset(cnt, 0, sizeof(cnt));
    for(int i = 1;i <= n;i ++) dist[i] = INF;
    dist[s] = 0;
    vis[s] = 1;
}
void spfa(int s){
    init(s);
    queue<int>q;
    q.push(s);
    while(!q.empty()){
        int p = q.front();
        vis[p] = 0;
        q.pop();
        for(int i = tail[p];~i;i = edge[i].next){
            int u = edge[i].to;
            if(dist[u] > dist[p] + edge[i].w){
                dist[u] = dist[p] + edge[i].w;
                if(!vis[u]){
                    vis[u] = 1;
                    q.push(u);
                }
            }
        }
    }
}
int aStar(int s, int t, int k){
    priority_queue<Node>Q;
    if(dist[s] == INF) return -1;
    Q.push(Node(s, 0, dist[s]));
    while(!Q.empty()){
        Node tt = Q.top();
        cnt[tt.p] ++ ;
        if(cnt[tt.p] > k) continue;
        if(cnt[tt.p] == k && tt.p == t) return tt.g+tt.h;
        Q.pop();
        for(int i = head[tt.p];~i;i = edge[i].next){
            int u = edge[i].to;
            Q.push(Node(u, tt.g+edge[i].w, dist[u]));
        }
    }
    return -1;
}
int main(){
    int s, t, k;
    int u, v, w;
    //freopen("in.c", "r", stdin);
    while(~scanf("%d%d", &n, &m)){
        memset(head, -1, sizeof(head));
        memset(tail, -1, sizeof(tail));
        k = 1;
        for(int i = 1;i <= m;i ++){
            scanf("%d%d%d", &u, &v, &w);
            addEdge(u, v, w, k);
            k += 2;
        }
        scanf("%d%d%d", &s, &t, &k);
        if(s == t) k++;
        spfa(t);
        int ans = aStar(s, t, k);
        printf("%d\n", ans);
    }
    return 0;
}