（poj 2449 Remmarguts' Date）<A*-K短路模板>

Solution

Code

// by spli
#include<cstring>
#include<cstdio>
#include<iostream>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;

const int N=1010;
const int M=100010;
int n,m,s,t,k;
struct node{
int to,nxt,val;
}e1[M],e2[M];int h1
,h2
,c1,c2;
int dis
;
bool vis
;
queue<int>q;
struct A{
int id,f,g;
bool operator <(const A &b)const{
return b.f==f?b.g<g:(b.f<f);
}
};
priority_queue<A>Q;

void add1(int f,int t,int v){
c1++;
e1[c1]=(node){t,h1[f],v};
h1[f]=c1;
}

void add2(int f,int t,int v){
c2++;
e2[c2]=(node){t,h2[f],v};
h2[f]=c2;
}

void spfa(){
memset(dis,0x7f,sizeof(dis));
dis[t]=0;vis[t]=1;q.push(t);
while(!q.empty()){
int u=q.front();
q.pop();
vis[u]=0;
for(int i=h2[u];i!=-1;i=e2[i].nxt){
int v=e2[i].to;
if(dis[v]>dis[u]+e2[i].val){
dis[v]=dis[u]+e2[i].val;
if(!vis[v]){
vis[v]=1;
q.push(v);
}
}
}
}
}

void A_star(){
int cnt=0;
int f,g;
if(s==t) k++;//可以说是很无耻了
Q.push((A){s,dis[s],0});
while(!Q.empty()){
A u=Q.top();

4000
Q.pop();
if(u.id==t){
cnt++;
if(cnt==k){
printf("%d\n",u.g);
return;
}
}
for(int i=h1[u.id];i!=-1;i=e1[i].nxt){
int v=e1[i].to;
g=u.g+e1[i].val;
f=g+dis[v];
Q.push((A){v,f,g});
}
}
printf("-1");
}

int main(){
memset(h1,-1,sizeof(h1));
memset(h2,-1,sizeof(h2));
scanf("%d%d",&n,&m);
int x,y,z;
for(int i=1;i<=m;++i){
scanf("%d%d%d",&x,&y,&z);
add1(x,y,z);add2(y,x,z);
}
scanf("%d%d%d",&s,&t,&k);
spfa();
A_star();
return 0;
}