hdoj 2199 Can you solve this equation? 【二分枚举】

#include <stdio.h>
#include <string.h>
#include <math.h>
#define eps 1e-10
#define f(x)  8*pow(x, 4) + 7*pow(x, 3) + 2*pow(x, 2) + 3*x
int main()
{
int t;
double n;
scanf("%d", &t);
while(t --){
scanf("%lf", &n);
n-=6;
double max = f(100);
if(n<0||n>max){
printf("No solution!\n");
continue;
}
double left, right, mid;
left = 0; right = 100;
while(right-left > 1e-7){  //精度要小于1e-7。
mid = (left+right)/2;
double temp = f(mid);
if(temp < n) left = mid+1e-7;
else right = mid;
}
printf("%0.4lf\n", left);
}
return 0;
}