bzoj4720: [Noip2016]换教室

dp裸题，求一遍floyd，dp式
f[i][j][0]=min(f[i-1][j][0]+(double)dis[c[i-1]][c[i]],f[i-1][j][1]+(1.0-k[i-1])(double)dis[c[i-1]][c[i]]+k[i-1](double)dis[d[i-1]][c[i]]);
f[i][j][1]=min(f[i-1][j-1][0]+(double)dis[c[i-1]][c[i]](1.0-k[i])+(double)dis[c[i-1]][d[i]]*k[i],f[i-1][j-1][1]+(double)dis[c[i-1]][c[i]](1.0-k[i])(1.0-k[i-1])+(double)dis[d[i-1]][d[i]]*k[i]*k[i-1]+(double)dis[c[i-1]][d[i]](1.0-k[i-1])k[i]+(double)dis[d[i-1]][c[i]]*k[i-1](1.0-k[i]));

#include
#include
#include
#include
#include
using namespace std;
int read()
{
    char ch=getchar();int f=0;
    while(ch<'0'||ch>'9')ch=getchar();
    while(ch>='0'&&ch<='9'){f=(f<<1)+(f<<3)+ch-'0';ch=getchar();}
    return f;
}
int n,m,v,e;
int dis[303][303],c[5003],d[5005];double k[5005],f[2005][2005][2];
int main()
{
    n=read(),m=read(),v=read(),e=read();
    for(int i=1;i<=v;i++)
    {
        for(int j=1;j<=v;j++)
        dis[i][j]=1000000000;
    }
    for(int i=1;i<=v;i++)
    dis[i][i]=0;
    for(int i=1;i<=n;i++)
    c[i]=read();
    for(int i=1;i<=n;i++)
    d[i]=read();
    for(int i=1;i<=n;i++)
    scanf("%lf",&k[i]);
    for(int i=1;i<=e;i++)
    {
        int u=read(),v=read(),w=read();
        dis[u][v]=min(dis[u][v],w);
        dis[v][u]=min(dis[v][u],w);
    }
    for(int k1=1;k1<=v;k1++)
    {
        for(int i=1;i<=v;i++)
        {
            for(int j=1;j<=v;j++)
            dis[i][j]=min(dis[i][j],dis[i][k1]+dis[k1][j]);
        }
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<=m;j++)
        f[i][j][0]=f[i][j][1]=2000000000;
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<=m;j++)
        {
            f[i][j][0]=min(f[i-1][j][0]+(double)dis[c[i-1]][c[i]],f[i-1][j][1]+(1.0-k[i-1])*(double)dis[c[i-1]][c[i]]+k[i-1]*(double)dis[d[i-1]][c[i]]);
            if(j)
            {
                f[i][j][1]=min(f[i-1][j-1][0]+(double)dis[c[i-1]][c[i]]*(1.0-k[i])+(double)dis[c[i-1]][d[i]]*k[i],f[i-1][j-1][1]+(double)dis[c[i-1]][c[i]]*(1.0-k[i])*(1.0-k[i-1])+(double)dis[d[i-1]][d[i]]*k[i]*k[i-1]+(double)dis[c[i-1]][d[i]]*(1.0-k[i-1])*k[i]+(double)dis[d[i-1]][c[i]]*k[i-1]*(1.0-k[i]));
            }
        }
    }
    double ans=2000000000;
    for(int i=0;i<=m;i++)
    {
        ans=min(ans,f[n][i][0]);
        ans=min(ans,f[n][i][1]);
    }
    printf("%.2lf",ans);
}