题目链接 http://www.acmore.net/problem.php?id=1494
#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
using namespace std;
int N,K;
double ai[1123456],bi[1123456],res[1123456],dp[1123456];
bool DO( double mid )
{
dp[0] = 0; res[0] = 0;
for( int i = 1; i <= N; i++ )
{
dp[i] = ai[i] - mid*bi[i];
res[i] = res[i-1] + dp[i];
}
for( int i = 1; i <= N; i++ )
dp[i] = max( dp[i],dp[i-1]+dp[i] );
for( int i = K; i <= N; i++ )
if( res[i] - res[i-K] + max( 0.,dp[i-K] ) >= 0 )
return true;
return false;
}
double search( double lt,double rt )
{
while( rt - lt > 0.00000001 )
{
double mid = ( lt + rt )/2.;
if( DO(mid) ) lt = mid;
else rt = mid;
}
return lt;
}
int main( )
{
while( scanf("%d%d",&N,&K) != EOF )
{
for( int i = 1; i <= N; i++ )
scanf("%lf",&ai[i]);
for( int j = 1; j <= N; j++ )
scanf("%lf",&bi[j]);
printf("%.4lf\n",search(0,1000));
}
return 0;
}