POJ - 2456 Aggressive cows

 1 #include <iostream>
 2 using namespace std;
 3 #include<string.h>
 4 #include<set>
 5 #include<stdio.h>
 6 #include<math.h>
 7 #include<queue>
 8 #include<map>
 9 #include<algorithm>
10 #include<cstdio>
11 #include<cmath>
12 #include<cstring>
13 #include <cstdio>
14 #include <cstdlib>
15 #include<stack>
16 #include<vector>
17 long long n,k;
18 long long a[110000];
19 long long panduan(long long zhi)
20 {
21     int add=1;
22     int kaishi=1,jieshu=1;
23     while(1)
24     {
25         if(a[jieshu]-a[kaishi]<zhi&&jieshu<=n)
26         {
27             jieshu++;
28         }
29         else if(a[jieshu]-a[kaishi]>=zhi)
30         {
31             add++;
32             kaishi=jieshu;
33         }
34         else
35             break;
36     }
37     //cout<<zhi<<"_"<<add<<endl;
38     return add;
39 }
40 int  main()
41 {
42     scanf("%lld %lld",&n,&k);
43     for(long long  i=1;i<=n;i++)
44         scanf("%lld",&a[i]);
45     sort(a+1,a+1+n);
46     long long kaishi=0,jieshu=1e18;
47     long long mid;
48     long long t;
49     while(kaishi<jieshu-1)
50     {
51         //cout<<kaishi<<"_"<<jieshu<<endl;
52         mid=(kaishi+jieshu)>>1;
53         if(panduan(mid)>=k)
54             kaishi=mid;
55         else
56             jieshu=mid;
57     }
58     cout<<kaishi<<endl;
59     return 0;
60 }