简单的递归转非递归例子 Fibonacci

package org.vocano.java.tst.recursion;

public class Fibonacci {
	
	public static int recursive(int n) {
		if(n < 2) return 1;
		return recursive(n-2) + recursive(n-1);
	}
	
	public static int directly(long n) {
		if(n < 3) return 1;
		int result = 0;
		int a1 = 1, a2 = 1;

		for (int i = 2; i <= n; i++) {
			result = a2 + a1;
			a1 = a2;
			a2 = result;
		}
		return result;
	}

	public static void main(String[] args) {
		long start = System.currentTimeMillis();
		System.out.println(recursive(40));
		long end = System.currentTimeMillis();
		System.out.println(end - start);
		System.out.println(directly(40));
		System.out.println(System.currentTimeMillis() - end);
	}
} /* output:
165580141
1401
-1109825406
0
*///:~