杭电 HDU ACM 2199 Can you solve this equation?

Can you solve this equation?

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 11180    Accepted Submission(s): 5151

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!

 

Author

Redow

 

 

搜索题，嗯， 这次知道了有个搜索名次，二分搜索。这样查找答案确实感觉特别妙。low 和high 无限夹逼答案。所以因为最后结果只需满足一定的精确度。这样可以找到合适的条件跳出while。

唉，如果不知道这样的话，浮点数暴力简直无语了都。

#include<iostream>#include<cmath>#include<stdio.h>using namespace std;double A(double x){    return (8*pow(x,4)+7*pow(x,3)+2*pow(x,2)+3*pow(x,1)+6);}int main(){    double  y;    int T;        cin>>T;    while(T--)    {        cin>>y;        if(A(0)>y||A(100)<y)        {            cout<<"No solution!"<<endl;            continue;        }        else{                double high,low,mid;        high=100;        low=0;            while(low+1e-8<high)            {                mid=(high+low)/2;                if(A(mid)>y)                    high=mid;                else                    low=mid;            }          printf("%.4lf\n",low);        }    }    return 0;}