POJ 3104 Drying(二分)

题目链接:http://poj.org/problem?id=3104

#include<stdio.h>
#include<algorithm>
#include<cmath>
#define INF 0x3f3f3f3f
using namespace std;
int n;
long long a[100005],k,l,r,sum,mid;
int main()
{
while(~scanf("%d",&n))
{
for(int i=0; i<n; i++)
scanf("%lld",&a[i]);
sort(a,a+n);
scanf("%lld",&k);
if(k==1)
{
printf("%lld\n",a[n-1]);
continue;
}
else
{
l=1;
r=a[n-1];
while(l<=r)
{
mid=(l+r)/2;
sum=0;
for(int i=0; i<n; i++)
if(a[i]>mid)
sum+=ceil((a[i]-mid)*1.0/(k-1));
if(sum<=mid)
r=mid-1;
else
l=mid+1;
}
}
printf("%lld\n",l);
}
return 0;
}