hdoj 2199 Can you solve this equation? 【二分基础题 注意去掉不满足的情况】

Can you solve this equation?

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

Total Submission(s): 13031    Accepted Submission(s): 5841

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!

 

看了一天网络流，做道简单点的题。

注意当Y < 6 || Y >= sum(100)时，没有解。。。

AC代码：

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>#define eps 1e-8using namespace std;double sum(double x){    return 8 * pow(x, 4) + 7 * pow(x, 3) + 2 * pow(x, 2) + 3 * x + 6 ;}int main(){    int t;    double Y;    scanf("%d", &t);    while(t--)    {        scanf("%lf", &Y);        if(Y < 6 || Y > sum(100))        {            printf("No solution!\n");            continue;        }        double left = 0, right = 100.0, mid;        while(right - left > eps)        {            mid = (left + right) / 2;            if(sum(mid) > Y)                right = mid;            else                left = mid;        }        printf("%.4lf\n", left);    }    return 0;}