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+7,mx=1e18;
LL read(){
    LL ans=0,c=getchar();
    while(c<'0'||c>'9') c=getchar();
    while(c>='0'&&c<='9'){ans=ans*10+(c-'0'); 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=1;i<=n;i++)if(k>=yy[i]){
        if(mx/w[i]<=k) return 1;
        if(sum>h[i]+w[i]*k) sum-=h[i]+w[i]*k;
        else return 1;
    }
    return sum<=0;
}
int main()
{
    freopen("tree.in","r",stdin);
    freopen("tree.out","w",stdout);
    n=read(); S=read(); mn=read();
    for(int i=1;i<=n;i++) h[i]=read();
    for(int i=1;i<=n;i++) w[i]=read();
    for(int i=1;i<=n;i++){
        LL now=mn-h[i];
        if(now%w[i]==0) yy[i]=now/w[i];
        else yy[i]=now/w[i]+1;
    }
    LL l=0,r=mx;
    while(l<=r){
        LL mid=(l+r)>>1;
        if(check(mid)) r=mid-1;
        else l=mid+1;    
    }
    printf("%lld
",l);
    return 0;
}