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?

斐波那契数列

class Solution {public:int climbStairs(int n) {if (n < 1)return 0;if (n == 1)return 1;if (n == 2)return 2;int a = 1, b = 2, res = 0;for (int i = 3; i <= n; i++) {res = a + b;a = b;b = res;}return res;}};