参考代码:
import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int n = scanner.nextInt(); double []arr = new double[n + 1]; double sum = 0; for(int i = 0; i <= n; i++) sum += 1 / factorial(arr, i); System.out.printf("%.10f", sum); } public static double factorial(double []arr, int n) { if(arr[n] != 0) return arr[n]; else if(n <= 1) { arr[n] = 1; return arr[n]; } arr[n] = factorial(arr, n - 1) * n; return arr[n]; } }
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