LeetCode 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?

题意： 求上n个台阶的方法数，要么走一步，要么两步。

思路：递归超时，递推

class Solution {public:    int climbStairs(int n) {        if (n <= 2) return n;        int f[1000];        f[1] = 1, f[2] = 2;        for (int i = 3; i <= n; i++)            f[i] = f[i-1] + f[i-2];        return f[n];    }};