【bzoj4590】[Shoi2015]自动刷题机

因为解一定是单调的，n越小切的题越多，这是可以肯定的，那么直接二分答案

#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
#include<queue>
using namespace std;
 
typedef long long LL;
 
#define INF 1LL<<60
#define N 100010
 
int n,k;
LL l,r,L,R;
 
LL a[N];
 
LL work(LL x)
{
    LL res(0),cnt(0);
    for (int i=1;i<=n;i++)
    {
        res=max(res+a[i],0LL);
        if (res>=x)
 
            res=0,cnt++;
    }
    return cnt;
}
 
int main()
{
    scanf("%d%d",&n,&k);
    for (int i=1;i<=n;i++)
        scanf("%lld",&a[i]);
    l=1;
    r=INF;
    while (l<=r)
    {
        LL m=(l+r)>>1;
        if (work(m)>k)
            L=m,l=m+1;
        else
            r=m-1;
    }
    l=1;
    r=INF;
    while (l<=r)
    {
        LL m=(l+r)>>1;
        if (work(m)<k)
            R=m,r=m-1;
        else
            l=m+1;
    }
    L++;
    R--;
    if (work(L)!=k || work(R)!=k)
        printf("-1
");
    else
        printf("%lld %lld",L,R);
    return 0;
}