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 1005struct 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;}
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