B

Can you solve this equation?

Time limit 1000 ms Memory limit 32768 kB OS Windows

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Problem Description

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.

Input

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);

Output

For each test case, you should just output one real number(accurate up to 4 decimal places),which is the solution of the equation,or “No solution!”,if there is no solution for the equation between 0 and 100.

Sample Input

2
100
-4

Sample Output

1.6152
No solution!

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题意：

方程8*x^4 + 7*x^3 + 2*x^2 + 3*x + 6 == Y，x属于[0，100]，输入Y，问是否存在这样的X满足上方程，若存在，输出X

解题思路：

直接对X进行二分就可以了，没什么好说的

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Code：

#include <iostream>#include <cmath>#include <cstdio>using namespace std;const double EPS=1e-5;double f(double x){    return 8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*x+6;}double bs(double Y){    double lo=0,hi=100,mid;    while(lo<hi)    {        mid=(hi+lo)/2.0;        if(fabs(Y-f(mid))<EPS)            return mid;        else if(f(mid)<Y)            lo=mid;        else            hi=mid;    }    return -1;}int main(){    int n;    cin>>n;    while(n--)    {        double Y;        cin>>Y;        double ans=bs(Y);        if(ans==-1)            cout<<"No solution!"<<endl;        else            printf("%.4f\n",ans);    }    return 0;}