Lightoj 1043 - Triangle Partitioning【二分】

题目链接：http://lightoj.com/volume_showproblem.php?

problem=1043

题意：一个三角形ABC，DE//BC。已知三角形ADE和四边形BDEC的面积的比，求AD的长度。

解法：二分AD边就可以

代码：

#include <stdio.h>
#include <ctime>
#include <math.h>
#include <limits.h>
#include <complex>
#include <string>
#include <functional>
#include <iterator>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <list>
#include <bitset>
#include <sstream>
#include <iomanip>
#include <fstream>
#include <iostream>
#include <ctime>
#include <cmath>
#include <cstring>
#include <cstdio>
#include <time.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>

using namespace std;

int main()
{
    int t; int cases = 1;

    double a, b, c, ratio;
    scanf("%d",&t);
    while (t--)
    {
        cin >> a >> b >> c >> ratio;

        double s = a*b;
        double ans;

        ratio = ratio / (ratio + 1.0);

        double left = 0, right = a;
        double mid;

        while (left + 0.000000001<= right)
        {
            mid = (left + right) / 2.0;
            ans = mid * b * (mid / a);
            ans /= s;

            if (ans >= ratio) right = mid;
            else left = mid;
        }

        printf("Case %d: ", cases++);
        printf("%.9lf\n", right);
    }
    return 0;
}