ZOJ3068 POJ2976 Dropping tests，二分检索

官方的解题报告可以看这里http://poj.org/showmessage?message_id=53194

我们可以看看如下推导

题目就变成了二分检索r

/*******************************************************************************
 # Author : Neo Fung
 # Email : [email protected]
 # Last modified: 2012-06-10 10:19
 # Filename: ZOJ3068 POJ2976 Dropping tests.cpp
 # Description : 
 ******************************************************************************/
#ifdef _MSC_VER
#define DEBUG
#define _CRT_SECURE_NO_DEPRECATE
#endif

#include <fstream>
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <string>
#include <limits.h>
#include <algorithm>
#include <math.h>
#include <numeric>
#include <functional>
#include <ctype.h>
using namespace std;

const int kMAX=10010;
const double kEPS=10E-5;

int main(void)
{
#ifdef DEBUG  
	freopen("../stdin.txt","r",stdin);
	freopen("../stdout.txt","w",stdout); 
#endif  

	int n,m,ncase=1;
	double num[kMAX],den[kMAX],scores[kMAX];

	while(~scanf("%d%d",&n,&m) && (m+n))
	{
		for(int i=0;i<n;++i)
			scanf("%lf",&num[i]);
		for(int i=0;i<n;++i)
			scanf("%lf",&den[i]);


		double lhs=0,rhs=1.0;

		while(lhs+kEPS<rhs)
		{
			double x=(lhs+rhs)/2;
			for(int i=0;i<n;++i)
				scores[i]=num[i]-den[i]*x;
			sort(scores,scores+n);
			double total=0.0;
			for(int i=m;i<n;++i)
				total+=scores[i];
			if(total>=0.0)
				lhs=x;
			else
				rhs=x;
		}
		printf("%d\n",int(100*lhs+0.5));
	}

	return 0;
}