Can you solve this equation?（二分）

Can you solve this equation?

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 32768/32768K (Java/Other)

Total Submission(s) : 61   Accepted Submission(s) : 37

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!

 

题解：二分法

代码：

#include<stdio.h>
double abs(double x){
    return x>0?x:-x;
}
double operate(double x){
    return  8*x*x*x*x+7*x*x*x+2*x*x+3*x+6.0; 
}
double search(double y){
    double l=0,r=100,mid;
    while(r-l>1e-10){mid=(l+r)/2;
        if(operate(mid)<y)l=mid;
        else r=mid;
        if(abs(operate(mid)-y)<1e-10)break;
    }
    return mid;
} 
int main(){
    int T;
    double Y;
    scanf("%d",&T);
    while(T--){
        scanf("%lf",&Y);
        if(Y<operate(0)||Y>operate(100))puts("No solution!");
        else printf("%.4lf
",search(Y));
    }
    return 0;
}