HDOJ2199Can you solve this equation?【二分查找】

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)

Total Submission(s): 12844    Accepted Submission(s): 5738

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!

 注意精度

#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>using namespace std;int main(){int i,j,t;double y,mid,a,b;scanf("%d",&t);while(t--){scanf("%lf",&y);a=0;b=100;double count;count=8.0*pow(100.0,4.0)+7.0*pow(100.0,3.0)+2.0*pow(100.0,2.0)+300.0+6.0;if(y-6.0000<1e-10||y-count>1e-10){printf("No solution!\n");continue;}while(b-a>1e-10){mid=(a+b)/2.0;count=8.0*pow(mid,4.0)+7.0*pow(mid,3.0)+2.0*pow(mid,2.0)+3.0*mid+6.0;if(count-y>1e-10)b=mid;else a=mid;}printf("%.4lf\n",mid);}return 0;}