[leetcode]70. Climbing Stairs

题目链接：https://leetcode.com/problems/climbing-stairs/#/description

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.

方法一：递归（超时）

class Solution{
public:
int climbStairs(int n)
{
if(n==1)
return 1;
if(n==2)
return 2;
return climbStairs(n-1)+climbStairs(n-2);
}
};

方法二：动态规划
class Solution{
public:
int climbStairs(int n)
{
vector<int> res(n+1,0);
res[0]=1;
res[1]=1;
for(int i=2;i<=n;i++)
{
res[i]=res[i-1]+res[i-2];
}
return res
;
}
};