洛谷新生舞会（错误代码

#include<iostream>
#include<cstdio>
#include<queue>
#include<algorithm>
#include<cmath>
#include<ctime>
#include<set>
#include<map>
#include<stack>
#include<cstring>
#define inf 2147483647
#define ls rt<<1
#define rs rt<<1|1
#define lson ls,nl,mid,l,r
#define rson rs,mid+1,nr,l,r
#define N 1100
#define For(i,a,b) for(long long i=a;i<=b;i++)
#define p(a) putchar(a)
#define g() getchar()

using namespace std;
long long n,s,t,tot;
long long a[N][N],b[N][N],d[N];
double l,r,mid,maxflow,mincost,eps=1e-8;
bool vis[N];
long long last[N],flow[N],pre[N],head[N];
struct node{
    long long n;
    long long v;
    double w;
    long long next;
}e[N];
queue<long long>q;
void in(long long &x){
    long long y=1;
    char c=g();x=0;
    while(c<'0'||c>'9'){
        if(c=='-')y=-1;
        c=g();
    }
    while(c<='9'&&c>='0'){
        x=(x<<1)+(x<<3)+c-'0';c=g();
    }
    x*=y;
}
void o(long long x){
    if(x<0){
        p('-');
        x=-x;
    }
    if(x>9)o(x/10);
    p(x%10+'0');
}

void push(long long x,long long y,long long v,double w){
    e[tot].n=y;
    e[tot].v=v;
    e[tot].w=w;
    e[tot].next=head[x];
    head[x]=tot++;

}

bool spfa(long long s,long long t){
    //memset(d,0,sizeof(d));
    memset(flow,0x7f,sizeof(flow));
    memset(vis,0,sizeof(vis));
    For(i,0,t)
        d[i]=0;
    q.push(s);
    vis[s]=1;
    d[s]=0;
    pre[t]=-1;
    while(!q.empty()){
        long long now=q.front();
        q.pop();
        vis[now]=0;
        for(long long i=head[now];i!=-1;i=e[i].next)
            if(e[i].v&&d[e[i].n]-d[now]-e[i].w<eps){
                d[e[i].n]d[now]+e[i].w;
                pre[e[i].n]=now;
                last[e[i].n]=i;
                flow[e[i].n]=min(flow[now],e[i].v);
                if(!vis[e[i].n]){
                    vis[e[i].n]=1;
                    q.push(e[i].n);
                }
            }
    }
    return pre[t]!=-1;
}

bool MCMF(long long s,long long t){
    while(spfa(s,t)){
        long long now=t;
        maxflow+=flow[t];
        mincost+=(double)flow[t]*d[t];
        while(now!=s){
            e[last[now]].v-=flow[t];
            e[last[now]^1].v+=flow[t];
            now=pre[now];
        }
    }
    return mincost>=0;
}

bool check(double c){
    s=0;t=2*n+1;
    memset(e,0,sizeof(e));
    memset(head,-1,sizeof(head));
    For(i,1,n){
        push(s,i,1,0);push(i+n,t,1,0);
    }
    For(i,1,n)
        For(j,1,n)
            push(i,j+n,1,a[i][j]-c*b[i][j]);
    return MCMF(s,t); 
}

int main(){
    in(n);
    For(i,1,n)
        For(j,1,n)
            cin>>a[i][j];
    For(i,1,n)
        For(j,1,n)
            cin>>b[i][j];
    l=0.0;r=900.0;
    while(r-l>eps){
        mid=(l+r)/2.0;
        if(check(mid))
            l=mid;
        else
            r=mid;
    }
    printf("%.6f",l);
    //cout<<l;
    return 0;
}