题目
July 6, 2021 · View on GitHub
The FORTH programming language does not support floating-point arithmetic at all. Its author, Chuck Moore, maintains that floating-point calculations are too slow and most of the time can be emulated by integers with proper scaling. For example, to calculate the area of the circle with the radius R he suggests to use formula like R * R * 355 / 113, which is in fact surprisingly accurate. The value of 355 / 113 ≈ 3.141593 is approximating the value of PI with the absolute error of only about 2*10-7 . You are to find the best integer approximation of a given floating-point number A within a given integer limit L. That is, to find such two integers N an
输入描述
The first line of input contains a floating-point number
输出描述
Output file must contain two integers, N and D, separated by space.
输入例子
3.14159265358979
10000
输出例子
355 113
参考答案
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
using namespace std;
struct Elem
{
int a, b;
}ans;
double n;
int lim;
int binarysearch(int x)
{
int l = 1;
int r = min(lim, x * 10);
while (l < r)
{
int mid = (l + r) / 2;
if (mid * 1.0 / x < n)
l = mid + 1;
else
r = mid;
}
return l;
}
void make(int a, int b)
{
if (abs(a * 1.0 / b - n) < abs(ans.a * 1.0 / ans.b - n))
{
ans.a = a;
ans.b = b;
}
}
int main()
{
scanf("%lf%d", &n, &lim);
ans.a = (int)(n + 0.5);
ans.b = 1;
if (ans.a == 0)
ans.a = 1;
if (ans.a > lim)
ans.a = lim;
for (int i = 2; i <= lim; i++)
{
int x = binarysearch(i);
make(x, i);
if (x > 1)
make(x - 1, i);
}
printf("%d %d\n", ans.a, ans.b);
return 0;
}