LeetCode Climbing Stairs 爬楼梯

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

 1 class Solution {
 2 public:
 3     int climbStairs(int n) {
 4         if(n==1) return 1;
 5         if(n==2) return 2;
 6         int a=1,b=2,c=0,i;
 7         for( i=0;i<n-2 ;i++ ){
 8             c=a+b;
 9             a=b;
10             b=c;
11         }
12         return c;
13     }
14 };