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?

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.
1. 1 step + 1 step + 1 step
2. 1 step + 2 steps
3. 2 steps + 1 step

 

Constraints:

• 1 <= n <= 45

Solution(javascript)

const climbStairs = (n) => {
  const memo = {}
  const aux = (count = 0) => {
    if (memo[count] !== undefined) {
      return memo[count]
    }
    if (count === n) {
      return 1
    }
    if (count > n) {
      return 0
    }
    memo[count] = aux(count + 1) + aux(count + 2)
    return memo[count]
  }
  return aux()
}