NUSOJ 2671 二分法应用之解方程

二分法应用之解方程8x^4 + 7x^3 + 2x^2 + 3x + 6
NUSOJ 2671

Problem：

Now,given the equation 8x^4 + 7x^3 + 2x^2 + 3x + 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!

题意：先输入t，代表有t个测试数据，然后输入测试的数也就是Y，然后根据8 * x^4 + 7 * x^3 + 2 * x^2 +3*x+ 6 = Y，求出x的值，很简单的二分题目。

#include<bits/stdc++.h>
using namespace std;

double vis(double y){
    return 8*pow(y,4)+7*pow(y,3)+2*pow(y,2)+3*y+6;
}

int main()
{
    int t;
    cin>>t; //t个测试数据
    while(t--){
          double y; 
           cin>>y;//x在1~100之间，y不会超过807020306，不会小于6
         if(y>807020306 || y<6) printf("langxinxuechang!\n");
         else {
            double left=0,right=100,mid;
            while(right-left>0.000000001){ 
             mid = left + (right-left)/2 ;

               if(vis(mid)==y) break;
               else if(vis(mid)>y) right = mid;
               else if(vis(mid)<y) left = mid;

            }
            printf("%.4f\n",mid);
         }




 }
    return 0;
}