随笔- 86 文章- 1 评论- 14 阅读- 12万

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;
        }
 
}