AtCoder Beginner Contest 063 D: Widespreader （二分答案）

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<stack>
#include<queue>
using namespace std;
typedef long long ll;

const int maxn = 100100;

int n;
ll A,B,tot,ma,cnt;
ll hel[maxn],hc[maxn];
ll read(){ ll s=0,f=1; char ch=getchar(); while(ch<‘0‘ || ch>‘9‘){ if(ch==‘-‘) f=-1; ch=getchar(); } while(ch>=‘0‘ && ch<=‘9‘){ s=s*10+ch-‘0‘; ch=getchar(); } return s*f; }

bool check(ll T){
    cnt=0;
    for(int i = 1; i <= n ; i++){
        hc[i]=hel[i]-1ll*T*B;
        if(hc[i]>0){
            if(hc[i]%(A-B)==0){
                cnt+=hc[i]/(A-B);
            }else{
                cnt+=(hc[i]/(A-B))+1;
            }
        }
    }
    return cnt<=T?true:false;
}

ll Binary_Search(){
    ll L=1,R=ma/B+1,ans;
    
    while(L<=R){
//        printf("%lld %lld\n",L,R);
        ll mid=(L+R)>>1;
        if(check(mid)) ans=mid,R=mid-1;
        else L=mid+1;
    }
    return ans;
}

int main(){
    tot=0; cnt=0; ma=0;
    n=read(),A=read(),B=read();
    
    for(int i=1;i<=n;i++){
        hel[i]=read();
        ma=max(ma,hel[i]);
    }
    
    printf("%lld",Binary_Search());
    
    return 0;
}