POJ 2449 Remmarguts' Date（A*+SPFA）K短路问题

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#include<stdio.h>
#include<string.h>
#include<queue>
#include<algorithm>
using namespace std;
#define INF 0x7ffffff
#define MAXM 100005
#define MAXN 1005
struct node
{
    int to,next,val;
}edge[MAXM],edge1[MAXM];
struct node1
{
    int g,h;
    int to;
    bool operator<(node1 a)const
    {
        if(a.h==h)return a.g<g;
        return a.h<h;
    }
};
int head[MAXN],head1[MAXN];
int dist[MAXN];
int vis[MAXN];
int Q[MAXM*5];
int n,m,k,k1;

void add(int x,int y,int val)
{
    edge[k].to=y;
    edge[k].val=val;
    edge[k].next=head[x];
    head[x]=k++;
}
void add1(int x,int y,int val)
{
    edge1[k1].to=y;
    edge1[k1].val=val;
    edge1[k1].next=head1[x];
    head1[x]=k1++;
}
void init()
{
    k=k1=0;
    memset(head,-1,sizeof(head));
    memset(head1,-1,sizeof(head1));
}
void spfa(int s)
{
    memset(vis,0,sizeof(vis));
    for(int i=1;i<=n;i++)
        dist[i]=INF;
    dist[s]=0;
    int h=0,t=1;
    Q[0]=s;
    vis[1]=1;
    while(h<t)
    {
        int now=Q[h++];
        vis[now]=0;
        for(int i=head1[now];i!=-1;i=edge1[i].next)
        {
            int w=edge1[i].to;
            if(dist[w]-dist[now]>edge1[i].val)
            {
                dist[w]=dist[now]+edge1[i].val;
                if(!vis[w])
                {
                    Q[t++]=w;
                    vis[w]=1;
                }
            }
        }
    }
}
int Astar(int s,int e,int kth)
{
    int cnt=0;
    priority_queue<node1>q;
    node1 now,next;
    now.to=s;
    now.g=0;
    now.h=dist[s];
    q.push(now);
    while(!q.empty())
    {
        next=q.top();
        q.pop();
        if(next.to==e)
        {
            cnt++;
            if(cnt==kth)return next.g;
        }
        for(int i=head[next.to];i!=-1;i=edge[i].next)
        {
            now.to=edge[i].to;
            now.g=next.g+edge[i].val;
            now.h=now.g+dist[now.to];
            q.push(now);
        }
    }
    return -1;
}
int main()
{
    init();
    scanf("%d%d",&n,&m);
    int a,b,v;
    int s,t,kth;
    for(int i=0;i<m;i++)
    {
        scanf("%d%d%d",&a,&b,&v);
        add(a,b,v);
        add1(b,a,v);
    }
    scanf("%d%d%d",&s,&t,&kth);
    if(s==t)kth++;
    spfa(t);
    int ans=Astar(s,t,kth);
    printf("%d\n",ans);
    return 0;
}