bzoj千题计划278：bzoj4590: [Shoi2015]自动刷题机

http://www.lydsy.com/JudgeOnline/problem.php?id=4590

二分

这么道水题 没long long WA了两发，没判-1WA了一发，二分写错WA了一发

最近是怎么了啊啊啊Ｏ(≧口≦)Ｏ

#include<cstdio>
#include<iostream>

using namespace std;

int n,m;

int x[100001];

void read(int &x)
{
    x=0; int f=1; char c=getchar();
    while(!isdigit(c)) { if(c=='-') f=-1; c=getchar(); }
    while(isdigit(c)) { x=x*10+c-'0'; c=getchar(); }
    x*=f;
}

int check(long long k)
{
    long long now=0;
    int sum=0;
    for(int i=1;i<=n;++i)
    {
        now+=x[i];
        if(now>=k) sum++,now=0;
        else if(now<0) now=0;
    }
    return sum;
}

int main()
{
    freopen("autoac.in","r",stdin);
    freopen("autoac.out","w",stdout);
    read(n); read(m);
    for(int i=1;i<=n;++i) read(x[i]);
    long long l=1,r=1LL*n*1e9,tmp=-1,mid;
    int t;
    while(l<=r)
    {
        mid=l+r>>1;
        t=check(mid);
        if(t==m) tmp=mid,r=mid-1;
        else if(t>m) l=mid+1;
        else r=mid-1;
    }
    if(tmp==-1) 
    {
        printf("-1");
        return 0;
    }
    cout<<tmp<<' ';
    l=tmp,r=1LL*n*1e9;
    while(l<=r)
    {
        mid=l+r>>1;
        t=check(mid);
        if(t==m) tmp=mid,l=mid+1;
        else if(t>m) l=mid+1;
        else r=mid-1;
    }
    cout<<tmp;
    return 0;
}