NYIST 914 Yougth的最大化

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <string>
 5 #include <cstdlib>
 6 #include <climits>
 7 #include <vector>
 8 #include <algorithm>
 9 #include <cmath>
10 #include <sstream>
11 using namespace std;
12 const double exps = 1e-3;
13 struct xyz {
14     int w,v;
15     double c;
16 } p[10010];
17 inline bool cmp(const xyz &a,const xyz &b) {
18     return a.c > b.c;
19 }
20 double ans(double t,const int &n,const int &k) {
21     int i,a = 0,b = 0;
22     double q = 0.0;
23     for(i = 0; i < n; i++)
24         p[i].c = p[i].v - t*p[i].w;
25     sort(p,p+n,cmp);
26     for(i = 0; i < k; i++) {
27         a += p[i].v;
28         b += p[i].w;
29     }
30     q = a*1.0/b;
31     if(fabs(q-t) < exps) return q;
32     return ans(q,n,k);
33 }
34 int main() {
35     int n,k,i;
36     while(~scanf("%d %d",&n,&k)) {
37         for(i = 0; i < n; i++)
38             scanf("%d %d",&p[i].w,&p[i].v);
39         printf("%.2f\n",ans(0.5,n,k));
40     }
41     return 0;
42 }