Codeforces 954 E. Water Taps

#include<cstdio>
#include<iostream>
#include<algorithm>

using namespace std;

#define N 200001

struct node
{
    int a,t;
}e[N],z[N],f[N];

void read(int &x)
{
    x=0; char c=getchar();
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) { x=x*10+c-‘0‘; c=getchar(); }
}

bool cmp1(node p,node q)
{
    return p.t<q.t;
}

bool cmp2(node p,node q)
{
    return p.t>q.t;
}

int main()
{
    int n,T;
    read(n); read(T);
    for(int i=1;i<=n;++i) read(e[i].a);
    for(int i=1;i<=n;++i) read(e[i].t);
    int cntz=0,cntf=0;
    double sum0=0,sum1=0; 
    int cnt0=0,cnt1=0;
    long long tot0=0,tot1=0;;
    for(int i=1;i<=n;++i) 
        if(e[i].t>=T) 
        {
            z[++cnt0]=e[i];
            sum0+=1LL*e[i].a*(e[i].t-T);
            tot0+=e[i].a;
        }
        else 
        {
            f[++cnt1]=e[i];
            sum1+=1LL*e[i].a*(T-e[i].t);
            tot1+=e[i].a;
        }
    sort(z+1,z+cnt0+1,cmp1);
    sort(f+1,f+cnt1+1,cmp2);
    double ans=0;
    if(sum0>=sum1)
    {
        ans=tot1;
        for(int i=1;i<=cnt0;++i)
            if(1.0*z[i].a*(z[i].t-T)<=sum1) 
            {
                sum1-=1.0*z[i].a*(z[i].t-T);
                ans+=z[i].a;
            }
            else 
            {
                ans+=sum1/(z[i].t-T);
                break;
            }
    }
    else
    {
        ans=tot0;
        for(int i=1;i<=cnt1;++i)
            if(1.0*f[i].a*(T-f[i].t)<=sum0)
            {
                sum0-=1.0*f[i].a*(T-f[i].t);
                ans+=f[i].a;
            }
            else
            {
                ans+=sum0/(T-f[i].t);
                break;
            }
    }
    printf("%.8lf",ans);
}