hdoj 2199 Can 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): 16603    Accepted Submission(s): 7372

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!

 

二分0~100  x的值，与y值比较

代码：

#include<cstdio>#include<cmath>int main(){int t;double y,sum;scanf("%d",&t);while(t--){scanf("%lf",&y);if(y<6.0||y>8.0*pow(100.0,4.0)+7.0*pow(100.0,3.0)+2.0*pow(100.0,2.0)+3.0*100.0+6.0)//排除非区间的结果{printf("No solution!\n");continue;}else{double l=0.0,r=100.0,mid;//int size=50;while(r-l>=1e-10){//printf("%.4lf\n",mid);mid=(l+r)/2.0;sum=8.0*pow(mid,4.0)+7.0*pow(mid,3.0)+2.0*pow(mid,2.0)+3.0*mid+6.0; if(sum<=y){l=mid;}else{r=mid;}}printf("%.4lf\n",l);}}return 0; }