[LeetCode]: 70: Climbing Stairs

题目：

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?

 

分析：

- 采用动态规划思想

- 将上楼过程分解为，"先上n-1梯，再上1梯" 和"先上n-2梯，再上2梯"这两个过程。

 

代码：

    public static int climbStairs(int n) {
        switch(n){
            case 1:
                return 1;
            case 2:
                return 2;
            default:
                int[] arrResult = new int[n+1];
                arrResult[0] = 1;
                arrResult[1] = 1;
                arrResult[2] = 2;
                
                for(int i = 3;i <= n;i++){
                    arrResult[i]=arrResult[i-1]/*最后剩一个楼梯*/ + arrResult[i-2] /*最后剩两个楼梯*/;
                }
                return arrResult[n];
        }
    }