leetcode 70

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?

此题为典型的菲波那切数列问题；

当n=1时，有1种走法；

当n=2时，有2种走法;

当n=3时，有3种走法;

当n=4时，有5种走法；

......

当n=k时，有你n[k-1] + n[k-2]种走法；

代码如下：

 class Solution {
 public:
     int climbStairs(int n) {
         if(n == )
         {
             return ;
         }
         if(n == )
         {
             return ;
         }
         int a = ;
         int b = ;
         int c;
         for(int i = ; i < n; i++)
         {
             c = a + b;
             a = b;
             b = c;
         }
         return c;
     }
 };