codeforces B. Okabe and Banana Trees 结论题

题目传送门

这道题 枚举一波y就好了 要求x，y整数 所以y最多1000个 然后算一波答案更新就好了 233

#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
using namespace std;
LL read(){
    LL 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;
}
LL m,b,ans;
int main()
{
    m=read(); b=read();
    for(LL y=b;y>=0;y--){
        LL x=m*b-m*y;
        LL sum1=(1+x)*x*(y+1)/2,sum2=(1+y)*y*(x+1)/2;
        ans=max(ans,sum1+sum2);
    }
    printf("%lld\n",ans);
    return 0;
}