阶乘

import java.util.Scanner;

/**
 * 输入n， 求 y1=1!+3!+...m!(m是小于等于n的最大奇数） y2=2!+4!+...p!(p是小于等于n的最大偶数)
 * 
 * @author kif
 *
 */
public class Factorial {

	// 最大奇数
	static int m;

	// 最大偶数
	static int p;
	
	/*
	 * 阶乘
	 */
	public static void factorial(int f , int m) {
		long sum = 0;
		for (; f <= m; f += 2) {
			long sum2 = 1;
			for (int j = 1; j <= f; j++) {
				sum2 *= j;
			}
			sum += sum2;
		}
		System.out.println(sum);
	}

	/*
	 * n的最大奇数阶乘
	 */
	public static void obbNumber(int m) {
		long sum = 0;
		for (int i = 1; i <= m; i += 2) {
			long sum2 = 1;
			for (int j = 1; j <= i; j++) {
				sum2 *= j;
			}
			sum += sum2;
		}
		System.out.println(sum);
	}

	/*
	 * n的最大偶数阶乘
	 * y2=2!+4!+...p!
	 */
	public static void evenNumber(int p) {
		long sum = 0;
		for (int i = 2; i <= p ; i += 2) {
			long sum2 = 1;
			for (int j = 1; j <= i; j++) {
				sum2 *= j;
			}
			sum += sum2;
		}
		System.out.println(sum);
	}

	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		System.out.print("请输入 n = ");
		int n = input.nextInt();
		if (n % 2 == 0) {
			p = n;
			m = n - 1;
		} else {
			m = n;
			p = n - 1;
		}
		System.out.println("p = " + p + "	m = " + m);
		Factorial.evenNumber(p);
		Factorial.obbNumber(m);
		Factorial.factorial(2, p);
		Factorial.factorial(1, m);
		input.close();
	}

}