codevs 1388 砍树

1388 砍树

二分

#include<cstdio>
using namespace std;
#define maxx(a,b) (a>b?a:b)
#define minn(a,b) (a>b?b:a)
#define LL long long
LL n,m,h[1000000+15];
inline void read(LL &now)
{
    char ch=getchar(); now=0;
    while(ch>'9'||ch<'0') ch=getchar();
    while(ch>='0'&&ch<='9') now=now*10+ch-'0',ch=getchar(); 
}

bool check(LL x)
{
    LL t=0,tot=0;
    for(int i=1;i<=n;i++)
        if(h[i]>x) tot+=h[i]-x;
    if(tot>=m) return true;
    return false;
}

int main()
{
    read(n); read(m);
    LL l=0,r=0;
    for(int i=1;i<=n;i++)
    {
        read(h[i]);
        r=maxx(r,h[i]);
        l=minn(l,h[i]);
    }
    while(l+1<r)
    {
        LL mid=(l+r)>>1;
        if(check(mid)) l=mid+1;
        else r=mid-1;
    }
    printf("%lld",l);
    return 0;
}