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2013
12-30

hdu 2199 Can you solve this equation?-分治-[解题报告]C++

Can you solve this equation?

问题描述 :

Now,given the equation 8*x^4 + 7*x^3 + 2*x^2 + 3*x + 6 == Y,can you find its solution between 0 and 100;
Now please try your lucky.

输入:

The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has a real number Y (fabs(Y) <= 1e10);

输出:

The first line of the input contains an integer T(1<=T<=100) which means the number of test cases. Then T lines follow, each line has a real number Y (fabs(Y) <= 1e10);

样例输入:

2
100
-4

样例输出:

1.6152
No solution!

#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;

const double eps=1e-10;

double y;

double f(double x){
    return 8*x*x*x*x+7*x*x*x+2*x*x+3*x+6-y;
}

int main(){

    //freopen("input.txt","r",stdin);

    int t;
    scanf("%d",&t);
    while(t--){
        scanf("%lf",&y);
        double l=0,r=100,mid;
        if(f(l)>eps || f(r)<eps){
            puts("No solution!");
            continue;
        }
        while(l+eps<=r){
            mid=(l+r)/2;
            if(f(mid)<eps)
                l=mid+eps;
            else
                r=mid-eps;
        }
        printf("%.4lf\n",l);
    }
    return 0;
}

解题转自:http://www.cnblogs.com/jackge/archive/2013/04/18/3029665.html