hd2199 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): 12911    Accepted Submission(s): 5776

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!
 
嗯，题目大意就是说对于上面的方程，给出一个y，求在1到100内满足方程等于y的x的值。
嗯，二分的最基本应用
#include<cstdio>#include<cstring>double f(double x){return 8*x*x*x*x+7*x*x*x+2*x*x+3*x+6;}double ans(double x){return x<0?-x:x;}int main(){int T;double left,right,mid,y;scanf("%d",&T);while(T--){scanf("%lf",&y);if(f(0)>y||f(100)<y){printf("No solution!\n");continue;}left=0;right=100;while(right-left>1e-10){mid=(left+right)/2;if(ans(f(mid)-y)<1e-10)break;if(f(mid)<y)left=mid;else right=mid;}printf("%.4lf\n",mid);}return 0;}