Java 解法, 执行用时: 1815ms, 内存消耗: 33048K, 提交时间: 2023-08-11 14:48:16

import java.util.*;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		while(sc.hasNext()) {
			double n = sc.nextLong();
			double r = n/2;
			double s = (Math.PI*r*r/2-n*n/4)*4;
			System.out.printf("%.6f\n", s);
		}
	}
}

Python3 解法, 执行用时: 652ms, 内存消耗: 6568K, 提交时间: 2023-08-11 14:46:54

import math
from sys import stdin, stdout

for line in stdin:
    n = int(line.strip())
    ans = (n**2 * math.pi) / 2 - n**2
    print('%.6f'%ans)

Python3 解法, 执行用时: 764ms, 内存消耗: 6384K, 提交时间: 2023-08-11 14:45:50

import math
n = open(0)
for i in n:
    out = 2 * math.pi * pow(int(i)/2, 2) - int(i) ** 2
    print(round(out, 6))