[leetcode] 70. Climbing Stairs

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?

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

用递归，显示运行超时。（很多运算重复了）

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

用数组保存，节省堆栈资源