UVA 10341

                                                                                    Solve It

Input:standard input

Output:standard output

Time Limit: 1 second

Memory Limit: 32 MB

Solve the equation:
        p*e^-x+q*sin(x) + r*cos(x) + s*tan(x) +t*x² + u = 0
        where 0 <= x <= 1.

Input

Input consists of multiple test cases and terminated by an EOF. Each test case consists of 6 integers in a single line:p, q,r, s,t and u (where0 <= p,r <= 20 and-20 <= q,s,t <= 0). There will be maximum 2100 lines in the input file.

Output

For each set of input, there should be a line containing the value ofx, correct upto 4 decimal places, or the string "No solution", whichever is applicable.

Sample Input

0 0 0 0 -2 1

1 0 0 0 -1 2

1 -1 1 -1 -1 1

Sample Output

0.7071

No solution

0.7554


函数单调递减  二分查找，高中知识，区间头尾对应的值相乘为负数，开始我分左右两边，用二分查找找他们相等，虽然给的样例过了，
但一直wa，也许是精度缺失了把，最后选择这样的

#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int p,q,r,s,t,u;
double fun(double x)
{
    double y;
    y = p*exp(-x)+q*sin(x)+r*cos(x)+s*tan(x)+t*x*x+u;
    return y;
}
int main()
{
    double m,n;
    while(cin>>p>>q>>r>>s>>t>>u)
    {
        double max=1.0;
        double min=0.0;
        if(fun(max)*fun(min)>0)
            cout<<"No solution"<<endl;
        else
        {
            double mid;
            while(min+0.00000001<=max)
            {
                mid=(max+min)/2.0;
                if(fun(mid)<=0)
                    max=mid;
                else
                    min=mid;
            }
            printf("%.4lf
",mid);
        }
    }
    return 0;
}