Find Nth Fibonacci number (Memoization)

Given a positive integer n, find the nth Fibonacci number. Fibonacci numbers, when it starts from 0, are calculaed as F(n), where F(1) = 0, F(2) = 1, and F(n) = F(n-1) + F(n-2) for n > 2. Example of first few Fibonacci numbers are 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.

Hint

This algorithm uses memoization to improve performance. It's same as the recursive version of Fibonacci, but with a special 'cache' to store results. The 'cache key' is crucial. It's how we identify and store past results. Sometimes we need one key, sometimes multiple keys. We add code to:

Initialize cache to store results.
Using the key to check cached result. If the result is not found in the cache, do the calculation and save the result in cache.
Return the cached result.

Python
Javascript

# Python implementation

cache = {}

def fib(n):
  if n < 2:
    return 0

  if n == 2:
    return 1

  if n not in cache:
    cache[n] = fib(n - 1) + fib(n - 2)

  return cache[n]

n = 5

print(fib(n))

// Javascript implementation

const cache = {}

function fib(n) {
  if (n < 2) {        
    return 0;
  }

  if (n == 2) {        
    return 1;
  }

  if (cache[n] === undefined) {
    cache[n] = fib(n - 1) + fib(n - 2);
  } 
  
  return cache[n];
}

const n = 5;

console.log(fib(n));