LeetCode:Climbing Stairs

 1 class Solution {
 2 public:
 3     int climbStairs(int n) {
 4         if(n==0)
 5             return 0;
 6         else if(n==1)
 7             return 1;
 8         else if(n==2)
 9             return 2;
10         else
11             return climbStairs(n-1)+climbStairs(n-2);
12     }
13 };

 1 class Solution {
 2     public:
 3         int climbStairs(int n) {
 4             if(n==0)
 5                 return 0;
 6             int a[n+1];
 7             a[0]=1;
 8             a[1]=1;
 9             for(int i=2;i<=n;i++)
10                 a[i]=a[i-1]+a[i-2];
11             return a[n];
12         }
13 };