算法学习01：算法-1步2步走台阶

 

Java深入学习19：算法-1步2步走台阶

 

如下

public class RrecursionTest {


    //题目：台阶共n层，每次只能走1步或2步，一共多少走法。

    //方案1-递归
    private static long f(long n){
        if(n == 1 || n == 2){
            return n;
        }
        return f(n-1) + f(n-2);
    }


    //方案2-循环
    private static long loop(long n){
        if(n == 1 || n == 2){
            return n;
        }

        long one = 2;
        long two = 1;
        long sum = 0;

        for(long i =3; i<n+1; i++){
            sum = one + two;
            two = one;
            one = sum;
        }
        return sum;
    }


    public static void main(String[] args) {
        long n = 50;
        long time1 = System.currentTimeMillis();
        System.out.println(f(n));
        long time2 = System.currentTimeMillis();
        System.out.println("f time: " + (time2 - time1));
        System.out.println(loop(n));
        long time3 = System.currentTimeMillis();
        System.out.println("loop time: " + (time3 - time2));
    }
}