J - AC自动机

P4343 [SHOI2015]自动刷题机

二分左右端点，验证答案，题意不是很清楚，导致一直没有写出来

#include<bits/stdc++.h>
using namespace std;

typedef long long LL;

const int N = 100010;
int a[N];
LL n,k;

int check(LL mid)
{
    
    LL res=0,sum=0;
    for(int i=1;i<=n;i++)
    {
    
        sum+=a[i];
        if(sum<0) sum=0;
        if(sum>=mid) res++,sum=0;
    }
    return res;
}
signed main()
{
    
	cin>>n>>k;
	for(int i=1;i<=n;i++) cin>>a[i];

	LL l,r;
	l=1,r=1e18;
	while(l<r)
	{
    
		LL mid=l+r>>1;
		if(check(mid)<=k) r=mid;
		else l=mid+1;
	}
	if(check(r)!=k) 
	{
    
		cout<<"-1";
		return 0;
	}
	cout<<l<<" ";
	
	l=1,r=1e18;
	while(l<r)
	{
    
		LL mid=l+r+1>>1;
		if(check(mid)>=k) l=mid;
		else r=mid-1;
	}
	cout<<l;
	
    return 0;
}