斐波那契数列实现

使用递归和非递归方式实现fibonacci数列，从输出结果分析：递归的执行效率低。

package com.sg.fibonacci;


public class FibonacciMain {

    public static void main(String[] args) {
        int num = 40;
        long begin = 0l;
        long end = 0l;
        
        begin= System.currentTimeMillis();
        System.out.print("Number "+num+" fibonacci value -> " +finnonacciTraversal(num));
        end = System.currentTimeMillis();
        System.out.println(" spend time: " + (end - begin));
        
        begin = System.currentTimeMillis();
        System.out.print("Number "+num+" fibonacci value -> " +fibonacciRecursive(num));
        end = System.currentTimeMillis();
        System.out.println(" spend time: " + (end - begin));
    }

    /**
     * 使用递归实现fibonacci数列
     * @param count 获取第count结果
     * @return
     */
    public static int fibonacciRecursive(int count){
        if(count == 1 || count == 2) {
            return 1;
        }else {
            int temp = fibonacciRecursive(count-1)+fibonacciRecursive(count-2);
            
            return temp;
        }
    }
    
    /**
     * 使用遍历的方式生成fibonacci数列
     * @param 获取第count结果
     * @return
     */
    public static int finnonacciTraversal(int count) {
        int f2 = 1;
        int f1 = 1;
        
        int temp = 0;
        for(int i=2;i<count;i++) {
            temp = f2;
            f2 = f1 + f2;
            f1 = temp;
        }
        
        return f2;
    }
}

 

Number 40 fibonacci value -> 102334155 spend time: 1
Number 40 fibonacci value -> 102334155 spend time: 811