【算法设计与分析基础】3、斐波拉契数列

package cn.xf.algorithm.ch02;

import java.util.Vector;

/**
 * 斐波那契数列
 * @author xiaof
 *
 */
public class Fib {
	
	/**
	 * 方式1，递归计算效率非常差双重指数级（不要问我怎么算的，我不会）
	 * 计算方法：百度=》带常系数的齐次二阶线性递推式
	 * @param n
	 * @return
	 */
	public static Long fib1(int n)
	{
		if(n <= 1)
			return (long) n;
		else
			return fib1(n - 1) + fib1(n - 2);
	}
	
	public static Long fib2(int n)
	{
		Long f0 = 0l;
		Long f1 = 1l;
//		Long fibn = f1 + f2;
		Long fibn = 0l;
		for(int i = 2; i <= n; ++i)
		{
			fibn = f0 + f1;
			f0 = f1;
			f1 = fibn; 
		}
		
		return fibn;
	}
	
	public static Vector<Long> fib3(int n)
	{
		Vector<Long> fib = new Vector<Long>();
		fib.setSize(n + 1);
		fib.set(0, 0l);
		fib.set(1, 1l);
		for(int i = 2; i <= n; ++i)
		{
			fib.set(i, fib.get(i - 1) + fib.get(i - 2));
		}
		
		return fib;
	}
	
	public static void main(String[] args) {
		System.out.println(Fib.fib1(10));
		System.out.println("******************************");
		System.out.println(Fib.fib2(10));
		System.out.println("******************************");
		Vector<Long> result = Fib.fib3(10);
		for(Long l : result)
		{
			System.out.print(l + "	");
		}
		
	}
}