Climbing Stairs
问题描述：
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.
测试代码（c++）：
class Solution {
public:
int climbStairs(int n) {
if(n<=2)
return n;
vector<int> dp(n,0);
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];
}
};