UVa 10341 (二分求根) Solve It

很水的一道题，因为你发现这个函数是单调递减的，所以二分法求出函数的根即可。

#include <cstdio>
#include <cmath>
//using namespace std;

const double e = 1e-14;
double p, q, r, s, t, u;

inline double f(double x)
{ return p*exp(-x) + q*sin(x) + r*cos(x) + s*tan(x) + t*x*x + u; }

int main()
{
    //freopen("in.txt", "r", stdin);

    while(scanf("%lf%lf%lf%lf%lf%lf", &p, &q, &r, &s, &t, &u) == 6)
    {
        if(f(0)<-e || f(1)>e) { puts("No solution"); continue; }
        double L = 0, R = 1, m;
        for(int i = 0; i < 30; i++)
        {
            m = (L+R)/2;
            if(f(m) < 0) R = m;
            else L = m;
        }
        printf("%.4f\n", m);
    }

    return 0;
}