Climbing Stairs

My Solution

Python

Iterative Approach

def climbStairs(n: int) -> int:
    seq = [2, 3]

    if n <= 3:
        return n

    for i in range(4, n+1):
        seq.append(seq[-1] + seq[-2])

    return seq[-1]

Memoized Recursive Approach (using Classes)

class Solution:
    def __init__(self):
        self.cache = {}


    def climbStairs(self, n: int) -> int:
        # Base Case
        if n <= 3:
            return n

        if n in self.cache:
            return self.cache[n]

        result = self.climbStairs(n-1) + self.climbStairs(n-2)
        self.cache[n] = result

        return result

JavaScript

Memoized Recursive Approach (using Closures)

const climbStairs = (function () {
  let cache = {};

  const func = function (n) {
    if (n <= 2) return 1;

    if (n in cache) {
      result = cache[n];
    } else {
      result = func(n - 1) + func(n - 2);
      cache[n] = result;
    }

    return result;
  };

  return func;
})();