POJ 1064 —— 二分

4 11
8.02
7.43
4.57
5.39

2.00

#include <cstdio>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <cstring>
#include <map>
#include <string>
#include <stack>
#include <cctype>
#include <vector>
#include <queue>
#include <set>
#include <utility>
#include <cassert>
using namespace std;
///#define Online_Judge
#define outstars cout << "***********************" << endl;
#define clr(a,b) memset(a,b,sizeof(a))
#define lson l , mid  , rt << 1
#define rson mid + 1 , r , rt << 1 | 1
#define mk make_pair
#define FOR(i , x , n) for(int i = (x) ; i < (n) ; i++)
#define FORR(i , x , n) for(int i = (x) ; i <= (n) ; i++)
#define REP(i , x , n) for(int i = (x) ; i > (n) ; i--)
#define REPP(i ,x , n) for(int i = (x) ; i >= (n) ; i--)
const int MAXN = 10000 + 50;
const int MAXS = 10000 + 50;
const int sigma_size = 26;
const long long LLMAX = 0x7fffffffffffffffLL;
const long long LLMIN = 0x8000000000000000LL;
const int INF = 0x7fffffff;
const int IMIN = 0x80000000;
const int inf = 1 << 30;
#define eps 1e-8
const long long MOD = 1000000000 + 7;
const int mod = 100000;
typedef long long LL;
const double PI = acos(-1.0);
typedef double D;
typedef pair<int , int> pii;
#define Bug(s) cout << "s = " << s << endl;
///#pragma comment(linker, "/STACK:102400000,102400000")
double l[MAXN];
int n , k;
int maxnum;
bool ok(int xx)
{
double x = xx / 1000.0;
int num = 0;
for(int i = 0  ;i < n ; i++)
{
num += (int)(l[i] / x);
}
return num >= k;
}
void solve()
{
int L = 0 , R = maxnum;
//    outstars
int ans = 0;
while(L <= R)
{
int mid = (L + R) >> 1;
if(ok(mid))
{
L = mid + 1;
ans = mid;
}
else R = mid - 1;
//        outstars
}
ans -= ans % 10;
printf("%.2lf\n" , ans / 1000.0);
}
int main()
{
while(~scanf("%d%d" , &n , &k))
{
maxnum = 0;
for(int i = 0 ; i < n ;i++)
{
scanf("%lf" , &l[i]);
maxnum = max(maxnum , (int)((l[i] + 0.0005) * 1000));
}

solve();
}
return 0;
}