HDU-2199 精度二分

最新推荐文章于 2021-08-25 20:34:03 发布

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最新推荐文章于 2021-08-25 20:34:03 发布

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分类专栏：二分文章标签：二分 hdu

本文链接：https://blog.youkuaiyun.com/qq_33914105/article/details/91616352

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本文介绍了一种使用二分法求解特定多项式方程在0到100区间内实数根的方法，通过示例输入输出展示了算法的实现过程，并提供了C++代码示例。

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Can you solve this equation?

HDU - 2199

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

2
100
-4

Sample Output

1.6152
No solution!

这题直接用二分做但要注意精度

#include<bits/stdc++.h>
using namespace std;
double y;
int n;
double fun(double x){
	return 8 * pow(x, 4) + 7 * pow(x, 3) + 2 * pow(x, 2) + 3 * x + 6;
}
int main(){
	cin >> n;
	while(n--){
		cin >> y;
		double l = 0;
		double r = 100;
		double mid;
		if(fun(0) > y || fun(100) < y)
	        cout << "No solution!" << endl;//函数单调性 手推一下就出来了
		else{
			while(r - l > 0.000001){
				mid = (l + r) / 2;
				if(fun(mid) - y > 0)
					r = mid + 0.0000001;
				if(fun(mid) - y < 0)
					l = mid - 0.0000001;

			}
			cout << fixed << setprecision(4) << (r + mid) / 2<< endl;//setprecision函数用法见我博客
		}
	}

}