BZOJ4590 SHOI2015自动刷题机（二分答案）

　　二分答案，分别往尽量小的和尽量大的二分即可。

#include<iostream> 
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
#define ll long long
#define N 100010
#define inf 100000000000000ll
int read()
{
    int x=0,f=1;char c=getchar();
    while (c<'0'||c>'9') {if (c=='-') f=-1;c=getchar();}
    while (c>='0'&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();
    return x*f;
}
char getc(){char c=getchar();while ((c<'A'||c>'Z')&&(c<'a'||c>'z')) c=getchar();return c;}
int gcd(int n,int m){return m==0?n:gcd(m,n%m);}
int n,m,a[N];
int calc(ll k)
{
    ll x=0;int cnt=0;
    for (int i=1;i<=n;i++)
    {
        x=max(0ll,x+a[i]);
        if (x>=k) cnt++,x=0;
    }
    return cnt;
}
int main()
{
#ifndef ONLINE_JUDGE
    freopen("bzoj4590.in","r",stdin);
    freopen("bzoj4590.out","w",stdout);
    const char LL[]="%I64d
";
#else
    const char LL[]="%lld
";
#endif
    n=read(),m=read();
    for (int i=1;i<=n;i++) a[i]=read();
    ll l=1,r=inf,ans=-1;
    while (l<=r)
    {
        ll mid=l+r>>1;
        if (calc(mid)<=m) ans=mid,r=mid-1;
        else l=mid+1;
    }
    if (calc(ans)!=m) ans=-1;
    cout<<ans<<' ';
    if (ans==-1) return 0;
    l=1,r=inf;
    while (l<=r)
    {
        ll mid=l+r>>1;
        if (calc(mid)>=m) ans=mid,l=mid+1;
        else r=mid-1;
    }
    cout<<ans;
    return 0;
}