HDOJ 2199 Can you solve this equation? (二分法)

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 13402    Accepted Submission(s): 5977

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!

 

 

 

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;double fx(double x){    return (8*x*x*x*x + 7*x*x*x + 2*x*x + 3*x + 6);}int main(){    int t;    while (scanf ("%d",&t)!=EOF)    {        while (t--)        {            double y,mid;            scanf ("%lf",&y);            double l=0;            double r=100;            if (y<6||y>fx(100))            printf ("No solution!\n");            else            {                while ((r-l)>1e-10)                {                    mid =(r+l)/2;                    if (fx(mid)>y)                        r=mid;                    else                        l=mid;                }                printf ("%.4lf\n",mid);            }                    }    }    return 0;}