BZOJ 4093: [Usaco2013 Dec]Vacation Planning

不难发现每条边都有交通中心所以对每个交通中心跑一次spfa就好

求答案的时候就枚举是先到哪个交通中心，取个最优值。

#include<cmath>
#include<queue>
#include<cstdio>
#include<vector>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#define me(a,x) memset(a,x,sizeof a)
using namespace std;
typedef long long LL;
const int N=20010,K=205;
const int inf=1000000007;
inline LL read()
{LL x=0,f=1; char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1; ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0'; ch=getchar();}return x*f;
}
struct node{int y,c,next;}a[N]; int first[N],len;
void ins(int x,int y,int c)
{a[++len].y=y,a[len].c=c,a[len].next=first[x],first[x]=len;
}
queue<int>q;
int f[K][N]; bool v[N];
int p[N];
void spfa(int st)
{q.push(st); me(v,0);v[st]=1,f[p[st]][st]=0;while(!q.empty()){int x=q.front();for(int k=first[x];k;k=a[k].next){int y=a[k].y;if(f[p[st]][y]>f[p[st]][x]+a[k].c){f[p[st]][y]=f[p[st]][x]+a[k].c;if(!v[y]){v[y]=1; q.push(y);}}}q.pop();v[x]=0;}
}
int main()
{int k=read(),m=read(),n=read(),q=read();int x,y,c,i;for(i=1;i<=m;i++){x=read(),y=read(),c=read();ins(x,y,c);}me(f,63);for(i=1;i<=n;i++){x=read();p[x]=i; spfa(x);}LL ans=0; int s=0;while(q--){x=read(),y=read();LL g=inf;if(!p[x])for(i=first[x];i;i=a[i].next)g=min(g,(LL)a[i].c+f[p[a[i].y]][y]);else g=f[p[x]][y];if(g<inf)s++,ans+=g;}printf("%d\n%lld\n",s,ans);return 0;
}

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