汕头市队赛 SRM13 T2

这道题很容易想到是二分但是因为可能会爆LL 所以要加一波特判
#include<cstdio>

#include<cstring>

#include<algorithm>

#define LL long long

using namespace std;

const LL M=1e6+,mx=1e18;

LL read(){

    LL ans=,c=getchar();

    while(c<''||c>'') c=getchar();

    while(c>=''&&c<=''){ans=ans*+(c-''); c=getchar();}

    return ans;

}

LL n,S,mn;

LL h[M],w[M],yy[M];

bool check(LL k){

    LL sum=S;

    for(int i=;i<=n;i++)if(k>=yy[i]){

        if(mx/w[i]<=k) return ;

        if(sum>h[i]+w[i]*k) sum-=h[i]+w[i]*k;

        else return ;

    }

    return sum<=;

}

int main()

{

    freopen("tree.in","r",stdin);

    freopen("tree.out","w",stdout);

    n=read(); S=read(); mn=read();

    for(int i=;i<=n;i++) h[i]=read();

    for(int i=;i<=n;i++) w[i]=read();

    for(int i=;i<=n;i++){

        LL now=mn-h[i];

        if(now%w[i]==) yy[i]=now/w[i];

        else yy[i]=now/w[i]+;

    }

    LL l=,r=mx;

    while(l<=r){

        LL mid=(l+r)>>;

        if(check(mid)) r=mid-;

        else l=mid+;

    }

    printf("%lld\n",l);

    return ;

}