Factorial数列的几种实现方式

斐波那契数列很常见，实现的方法主要有递归，for，栈等，下面给出代码

import java.math.BigInteger;
import java.util.Scanner;
import java.util.Stack;

public class NFactorial {
	public static void main(String[] args) {
		System.out.println("请输入一个数：");
		Scanner sc= new Scanner(System.in);
		int q =sc.nextInt();

		System.out.println("递归结果："+factorial(q));
		System.out.println("5的递归结果："+factorial(new BigInteger("5")));
		System.out.println("栈运算结果："+factorial_stack(q));
		System.out.println("for运算结果："+factorial_for(q));
	}
/*
 * 用递归实现
 * */
	private static int factorial(int n){
		if(n==0){
			return 0;
		}
		if(n==1){
			return 1;
		}
		else{
			int temp =n*factorial(n-1);

		return temp;
		}
	}

	private static BigInteger factorial(BigInteger n){
		if(n.compareTo(BigInteger.ONE)==-1){
			return BigInteger.ZERO;
		}
		if(n.compareTo(BigInteger.ONE)==0){
			return BigInteger.ONE;
		}
		else{
			BigInteger temp =n.multiply(factorial(n.subtract(BigInteger.ONE)));
		return temp;
		}
	}

	/*
	 * 用栈实现
	 * */
	private static BigInteger factorial_stack(int n){
		Stack stk=new Stack();
		BigInteger num=BigInteger.ONE;
		for(int i=1;i<=n;i++){
			stk.push(i);
		}
		while (stk.size()>0){
			BigInteger bign=new BigInteger(stk.pop().toString());
			num=num.multiply(bign);
		}
		return num;
		}	

	/*
	 * 用for实现
	 * */
		private static BigInteger factorial_for(int n){
			BigInteger num=BigInteger.ONE;
			for(int i=1;i<=n;i++){
				BigInteger bign = new BigInteger(String.valueOf(i));
				num=num.multiply(bign);
			}
			return num;
		}

}