70. 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?

Note: Given n will be a positive integer.

题目含义：n层高的梯子，每一步能爬1层或2层，问从底爬到顶端有多少种爬法

 1     public int climbStairs(int n) {
 2         if (n==1) return 1;
 3         else if (n==2) return 2;
 4 //        return climbStairs(n-1) + climbStairs(n-2);        //递归方式会超时
 5         int[] dp = new int[n];
 6         dp[0] = 1; dp[1] = 2;
 7         for (int i = 2; i < n; ++i) {
 8             dp[i] = dp[i - 1] + dp[i - 2];
 9         }
10         return dp[n - 1];  
11     }

 

posted @ 2017-10-18 17:14  daniel456  阅读(123)  评论(0)  编辑  收藏  举报