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?
Note: Given n will be a positive integer.
题解：
爬到第n层的方法要么是从第n-1层一步上来的，要不就是从n-2层2步上来的
Solution 1 ()
class Solution { public: int climbStairs(int n) { vector<int> dp(n,0); if(n<2) return n; dp[0] = 1; dp[1] = 2; for(int i=2; i<n; i++) { dp[i] = dp[i-2] + dp[i-1]; } return dp[n-1]; } };
Solution 2 ()
class Solution { public: int climbStairs(int n) { if(n<2) return n; int a = 1; int b = 2; for(int i=2; i<n; i++) { b += a; a = b - a; } return b; } };
【LeetCode】070. Climbing Stairs
原文：http://www.cnblogs.com/Atanisi/p/6817390.html