POJ2456 Aggressive cows

　　Aggressive cows

　　二分，关键是转化为二分！

 #include <cstdio>
 #include <algorithm>
 const int maxn = ;
 const int maxN = ;

 int N, C;
 int a[maxN];
 using namespace std;
 bool judge(int x) {
     int s = ;
     for (int i = ; i < C;i++) {
         int ctr = s+;
         while (ctr < N && (a[ctr]-a[s] < x)) {
             ctr++;
         }
         if (ctr==N) {
             return false;
         }
         s = ctr;
     }
     return true;
 }
 int main(void)
 {
     scanf("%d%d", &N, &C);
     for (int i = ; i < N; i++) {
         scanf("%d", &a[i]);
     }
     sort(a, a+N);
     int l = , u = maxn, mid;
     for (;(u-l)>;){
         mid = (l+u)/;
         if (judge(mid)) {
             l = mid;
         } else {
             u = mid;
         }
     }
     printf("%d\n", l);
     return ;
 }