BZOJ 4720: [Noip2016]换教室

错是被学长挑出来的。。。QWQ@Monster_Yi

f[i][j][0/1] 为 第i天，换j次，换1/没换0

然后大力DP

#include<cstdio>
#include<iostream>
#include<cstring>
#define R register int
using namespace std;
struct node{
    int c,d;
    #define c(i) a[i].c
    #define d(i) a[i].d
}a[10010];
int n,m,v,ee;
long long e[310][310];
double k[2010],f[2010][2010][2],ans=1e17+10;
inline void floyed() {for(R k=1;k<=v;++k) for(R i=1;i<=v;++i) for(R j=1;j<=v;++j) e[i][j]=min(e[i][j],e[i][k]+e[k][j]);}
signed main() {
    scanf("%d%d%d%d",&n,&m,&v,&ee);
    for(R i=1;i<=n;++i) scanf("%d",&c(i)); for(R i=1;i<=n;++i) scanf("%d",&d(i)); for(R i=1;i<=n;++i) scanf("%lf",&k[i]);
    memset(e,0x3f,sizeof e); for(R i=1,u,vv,w;i<=ee;++i) scanf("%d%d%d",&u,&vv,&w),e[u][vv]=e[vv][u]=min(e[u][vv],(long long)w);
    for(R i=1;i<=v;++i) e[i][i]=0; floyed(); //for(R i=1;i<=v;++i,cout<<endl)for(R j=1;j<=v;++j) cout<<e[i][j]<<" ";
    for(R i=0;i<=n;++i) for(R j=0;j<=n;++j) f[i][j][1]=f[i][j][0]=1e17+10; f[1][0][0]=f[1][1][1]=0;
    for(R i=2;i<=n;++i) { f[i][0][0]=f[i-1][0][0]+e[c(i)][c(i-1)];
        for(R j=1;j<=min(i,m);++j){
            f[i][j][0]=min(f[i][j][0],min(f[i-1][j][0]+e[c(i)][c(i-1)],f[i-1][j][1]+k[i-1]*e[c(i)][d(i-1)]+(1-k[i-1])*e[c(i)][c(i-1)]));
            f[i][j][1]=min(f[i][j][1],min(f[i-1][j-1][0]+k[i]*e[d(i)][c(i-1)]+(1-k[i])*e[c(i)][c(i-1)],
                           f[i-1][j-1][1]+k[i-1]*k[i]*e[d(i)][d(i-1)]+(1-k[i])*(1-k[i-1])*e[c(i)][c(i-1)]+k[i]*(1-k[i-1])*e[d(i)][c(i-1)]+(1-k[i])*k[i-1]*e[c(i)][d(i-1)]));
        }
    } for(R i=0;i<=m;++i) ans=min(min(f[n][i][0],f[n][i][1]),ans);//,cout<<f[n][i][0]<<" "<<f[n][i][1]<<endl;
    printf("%.2lf\n",ans);
}

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2019.04.07