HDU2199：Can you solve this equation?(二分)

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

2100-4

 

Sample Output

1.6152No solution!

 

 

一开始跑去百度一元四次方程的解，直接就被吓尿了，然后知道用二分做之后，发现二分还能解决这样的题目，数学无法做到的事情用程序可以很简单的就做到了

 

#include <stdio.h>#include <math.h>#include <algorithm>#include <string.h>#include <math.h>using namespace std;double cal(double x){    return 8*x*x*x*x+7*x*x*x+2*x*x+3*x+6;}int main(){    int t;    scanf("%d",&t);    while(t--)    {        double n;        scanf("%lf",&n);        if(cal(0)>n || cal(100)<n)        {            printf("No solution!\n");            continue;        }        double l = 0.0,r = 100.0;        double mid = (l+r)/2;        while(fabs(cal(mid)-n)>1e-5)        {            if(cal(mid)>n)                r = mid-1;            else                l = mid+1;            mid = (l+r)/2;        }        printf("%.4f\n",mid);    }    return 0;}