POJ3104Drying(二分)

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define N 100009
using namespace std;

int n;

int a[N];

int k,ans;

bool ok(int x)
{
    int js=0;
    for(int i=1;i<=n;i++)
    {
        if(a[i]<=x) continue;
        js=js+(a[i]-x+k-2)/(k-1);
        if(js>x) return false;
    }
    return true;
}

int main()
{
    scanf("%d",&n);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    scanf("%d",&k);
    sort(a+1,a+n+1);
    int L=1,R=a[n];
    if(k==1)
    {
        cout<<a[n]<<endl;
        return 0;
    }
    while(L<=R)
    {
        int mid=(L+R)>>1;
        if(ok(mid))
        {
            ans=mid;
            R=mid-1;
        }else L=mid+1;
    }
    cout<<ans<<endl;
    return 0;
}