poj 2456 Aggressive cows 二分

 1 #include <iostream>
 2 #include <vector>
 3 #include <math.h>
 4 #include <algorithm>
 5 
 6 
 7 using namespace std;
 8 
 9 /*
10 Sample Input
11 5 3
12 1
13 2
14 8
15 4
16 9
17 Sample Output
18 3
19 */
20 
21 
22 vector<int> v;
23 
24 int n, m;
25 
26 
27 bool check(int d)
28 {
29     int mm=m-1;
30 
31     int lastselect = v[0];
32 
33     for (int i = 1; i < n; i++) {
34         if (v[i] - lastselect >= d) {
35             mm--;
36             lastselect = v[i];
37             if (mm == 0)
38                 return false;
39         }
40     }
41 
42     return true;
43 }
44 
45 
46 
47 
48 int main()
49 {
50     cin >> n >> m;
51 
52     for (int i = 0; i < n; i++) {
53         int t; cin >> t;
54         v.push_back(t);
55     }
56     if (m == 1) {
57         printf("0\n");
58         return 0;
59     }
60 
61     sort(v.begin(), v.end());
62 
63     //距离的极端取值k
64     int l = 0; int r = v.back();
65 
66     while (l<r) {
67         int mid = l + r >> 1;
68         if (check(mid)) r = mid;
69         else {
70             l = mid + 1;
71         }
72     }
73 
74     cout << r-1 << endl;
75 
76     return 0;
77 }