AtCoder Regular Contest 075 D Widespread

题目传送门

这道题其实二分一下答案就okay了的 不过LL什么的有时候忘了加 被卡了下

#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
using namespace std;
const int M=100007;
int read(){
    int ans=0,f=1,c=getchar();
    while(c<'0'||c>'9'){if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9'){ans=ans*10+(c-'0'); c=getchar();}
    return ans*f;
}
int n,p,q,w;
int s[M];
LL ans;
bool check(LL x){
    LL now=x*q,tot=0;
    int top=n,v;
    while(top){
        if(s[top]<=now) break;
        if((s[top]-now)%w) v=(s[top]-now)/w+1;
        else v=(s[top]-now)/w;
        tot+=v;
        top--; 
    }
    return tot<=x;
}
int main()
{
    n=read(); p=read(); q=read(); w=p-q;
    for(int i=1;i<=n;i++) s[i]=read();
    sort(s+1,s+1+n);
    LL l=0,r=1e9;
    while(l<=r){
        LL mid=(l+r)>>1;
        if(check(mid)) ans=mid,r=mid-1;
        else l=mid+1;
    }
    printf("%lld\n",ans);
    return 0;
}