poj2976 Dropping tests（01分数规划 好题）

https://vjudge.net/problem/POJ-2976

又是一波c++AC,g++WA的题。。

先推导公式：由题意得 Σa[i]/Σb[i]<=x，二分求最大x。化简为Σ(a[i]-x*b[i])<=0，按a[i]-x*b[i]降序排列，从中取前n-m个和满足该式的话，就说明x多半是偏大了。

 #include<iostream>
 #include<cstdio>
 #include<queue>
 #include<cstring>
 #include<algorithm>
 #include<cmath>
 #include<map>
 #define lson l, m, rt<<1
 #define rson m+1, r, rt<<1|1
 #define INF 0x3f3f3f3f
 typedef long long ll;
 using namespace std;
 ll a[], b[];
 double c[];
 ll n, m;
 bool cmp(const double a, const double b)
 {
     return a>b;
 }
 int C(double x)
 {
     for(int i = ; i < n; i++){
         c[i] = a[i]-x*b[i];
     }
     sort(c, c+n, cmp);//降序
     double ans=;
     for(int i = ; i < n-m; i++){
         ans += c[i];
     }
     return ans<=;//
 }
 int main()
 {
     while(~scanf("%lld%lld", &n, &m)){
         if(!n&&!m) break;
         for(int i = ; i < n; i++){
             scanf("%lld", &a[i]);
         }
         for(int i = ; i < n; i++){
             scanf("%lld", &b[i]);
         }
         double lb = , ub = ;
         for(int i = ; i < ; i++){
         //while(ub-lb>1e-6){
             double mid = (ub+lb)/;
             if(C(mid)){
                 ub = mid;
             }
             else lb = mid;
             //cout << mid << endl;
         }
         printf("%.0lf\n", (ub*));
     }
     return ;
 }