BZOJ_4819_[Sdoi2017]新生舞会_01分数规划+费用流

#include <stdio.h>
#include <string.h>
#include <algorithm>
using namespace std;
typedef double f2;
#define N 250
#define M 500050
#define S (n+n+1)
#define T (n+n+2)
int head[N],to[M],nxt[M],flow[M],cnt=1,n,a[105][105],b[105][105],Q[N],l,r;
int inq[N],path[N];
f2 val[M],dis[N];
inline void add(int u,int v,int f,f2 va) {
    to[++cnt]=v; nxt[cnt]=head[u]; head[u]=cnt; flow[cnt]=f; val[cnt]=va;   
    to[++cnt]=u; nxt[cnt]=head[v]; head[v]=cnt; flow[cnt]=0; val[cnt]=-va;
}
bool spfa() {
    memset(dis,0xc2,sizeof(dis));
    memset(path,0,sizeof(path));
    dis[S]=0;inq[S]=1;l=r=0;Q[r++]=S;
    while(l!=r) {
        int x=Q[l++],i;if(l==S) l=0; inq[x]=0;
        for(i=head[x];i;i=nxt[i]) {
            if(dis[to[i]]<dis[x]+val[i]&&flow[i]) {
                dis[to[i]]=dis[x]+val[i];
                path[to[i]]=i^1;
                if(!inq[to[i]]) {
                    inq[to[i]]=1; Q[r++]=to[i]; if(r==S) r=0;
                }
            }
        }
    }
    return path[T];
}
bool check(f2 x) {
    int i,j;
    memset(head,0,sizeof(head)); cnt=1;
 
    for(i=1;i<=n;i++) {
        add(S,i,1,0.0);
        add(i+n,T,1,0.0);
    }
    for(i=1;i<=n;i++) {
        for(j=1;j<=n;j++) {
            add(i,n+j,1,a[i][j]-x*b[i][j]);
        }
    }
    f2 maxc=0;
    while(spfa()) {
        int i,nf=1<<30;
        for(i=T;i!=S;i=to[path[i]]) {
            nf=min(nf,flow[path[i]^1]);
        }
        for(i=T;i!=S;i=to[path[i]]) {
            flow[path[i]]+=nf;
            flow[path[i]^1]-=nf;
            maxc+=nf*val[path[i]^1];
        }
    }
    return maxc>=0;
}
int main() {
    scanf("%d",&n);
    int i,j;
    for(i=1;i<=n;i++) {
        for(j=1;j<=n;j++) {
            scanf("%d",&a[i][j]);
        }
    }
    for(i=1;i<=n;i++) {
        for(j=1;j<=n;j++) {
            scanf("%d",&b[i][j]);
        }
    }
    f2 ll=0,rr=1000000;
    for(i=1;i<=60;i++) {
        f2 mid=(ll+rr)/2;
        if(check(mid)) ll=mid;
        else rr=mid;
    }
    printf("%.6lf\n",ll);
}