BestCoder Round #55 1001 Pyramid Split

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5432

裸的二分查找，同时注意向下取整

#include <iostream>
#include <cstdio>
#include <algorithm>

using namespace std;

#define maxn 100000+5
const double exps = 1e-6;

int t,n;

struct node
{
    double h,w;
}a[maxn];


int main()
{
    scanf( "%d",&t );
    while( t-- )
    {
        scanf( "%d",&n );
        for( int i=0; i<n; i++ )
            scanf( "%lf",&a[i].h );
        for( int i=0; i<n; i++ )
        {
            scanf( "%lf",&a[i].w );
        }
        double L = 0, R = 1000, mid;
        while( R - L > exps)
            {
            mid = (L + R) / 2;
            double s, sum1 = 0, sum2 = 0;
            for(int j = 0; j < n; j++)
            {

                if(a[j].h <= mid) s = 0;
                else s = a[j].w * a[j].w * (a[j].h- mid) * (a[j].h - mid) * (a[j].h - mid) / (3.0 * a[j].h * a[j].h);
                sum1 += s;
                sum2 += a[j].w * a[j].w * a[j].h / 3.0 - s;
            }

            if(sum1 < sum2) R = mid;
            else L = mid;
        }
        printf("%d
", (int)mid);
    }
    return 0;
}