poj 2976 Dropping tests 01分数规划

题目大意:

http://poj.org/problem?id=2976

题解:

裸的01分数规划

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
inline void read(int &x){
	x=0;char ch;bool flag = false;
	while(ch=getchar(),ch<'!');if(ch == '-') ch=getchar(),flag = true;
	while(x=10*x+ch-'0',ch=getchar(),ch>'!');if(flag) x=-x;
}
const int maxn = 1024;
const double eps = 1e-9;
inline int dcmp(const double &x){
	if(x < eps  && x > -eps) return 0;
	return x > 0 ? 1 : -1;
}
int a[maxn],b[maxn];
double d[maxn];
int main(){
	int n,m;
	while(1){
		read(n);read(m);m = n - m;
		if(n == 0 && m == 0) break;
		for(int i=1;i<=n;++i) read(a[i]);
		double l = 0,r = 0;
		for(int i=1;i<=n;++i){
			read(b[i]); 
			r = max(r,(double)a[i]/b[i]);
		}
		while((r-l) > eps){
			double mid = (l+r)/2;
			for(int i=1;i<=n;++i) d[i] = a[i] - mid*b[i];
			sort(d+1,d+n+1);double sum = 0;
			for(int i=n;i>=n-m+1;--i) sum += d[i];
			if(dcmp(sum) >= 1) l = mid;
			else r = mid;
		}
		printf("%d
",(int)(l*100.0 + 0.5) );
	}

	getchar();getchar();
	return 0;
}