Climbing Stairs

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

只计算爬楼方法：

java代码

int climbStairs(int n) {
    if (n <= 1)
        return 1;

    int a = 1, b = 1, c = 1;
    for (int i = 2; i <= n; ++i) {
        c = a + b;
        a = b;
        b = c;
    }
    return c;
}

输出n层楼的爬楼方式

java代码

List<String> climbStairsWay(int n) {
    List<String> res = new ArrayList<>();
    if(n<=0)
        return res;

    List<String> last = new ArrayList<String>();
    last.add("1");
    if(n==1){
        return last;
    }

    List<String> secondLast = new ArrayList<String>();
    secondLast.add("1,1");
    secondLast.add("2");
    if(n==2) {
        return secondLast;
    }

    for(int i=3;i<=n;i++) {
        for(String temp : secondLast) {
            res.add("1," + temp);
        }

        for(String temp : last) {
            res.add("2," + temp);
        }

        if(i<n) {
            last = secondLast;
            secondLast = res;
            res = new ArrayList<>();
        }
    }

    return res;
}