70. Climbing Stairs（Easy）

原题目：

　　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.

　

题目大意如下：

　　每次只能爬一步或者两步梯子，问总共有多少种方法可以爬到顶端。

解题思路：

　　动态规划。状态转移方程：c[i] = c[i-1] + c[i-2] （ n >= 2）;

代码如下：

class Solution {
public:
int climbStairs(int n) {
int c[n+1] ;
memset(c , 0 , sizeof(c)) ;
if(n == 0) return 0 ;
if(n == 1) return 1 ;
if(n == 2) return 2 ;
c[0] = 0 ;
c[1] = 1 ;
c[2] = 2 ;
for(int i = 3 ; i < n+1 ; ++i)
c[i] = c[i-1] + c[i-2] ;
return c
;
}
};