leetcode刷题笔记(Golang)--70. Climbing Stairs

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?

Note: Given n will be a positive integer.

Example 1:

Input: 2
Output: 2
Explanation: There are two ways to climb to the top.

1. 1 step + 1 step
2. 2 steps
   Example 2:

Input: 3
Output: 3
Explanation: There are three ways to climb to the top.
3. 1 step + 1 step + 1 step
4. 1 step + 2 steps
5. 2 steps + 1 step

func climbStairs(n int) int {
	if n <= 0 {
		return 0
	}
	if n == 1 {
		return 1
	}
	if n == 2 {
		return 2
	}
	res := make([]int, n+1)
	res[1] = 1
	res[2] = 2
	for i := 3; i <= n; i++ {
		res[i] = res[i-1] + res[i-2]
	}
	return res[n]    
    
}