Question 76

Question

Describe the concept of memoization and its implementation in JavaScript.

Answer

What is Memoization?

Memoization is a caching strategy that stores the results of expensive function calls and returns the cached result if the same inputs occur again. Think of it like remembering previous answers to save time on repeated calculations.

Benefits:

• Performance Boost: Significantly speeds up programs by avoiding redundant computations, especially for functions with repetitive input patterns.

• Efficiency: Reduces resource consumption (CPU time and memory) as you're not recalculating values.

JavaScript Implementation:

function memoizedFibonacci(n, cache = {}) {
  if (n in cache) {
    return cache[n]; 
  }
  if (n <= 1) {
    return n;
  }
  cache[n] = memoizedFibonacci(n - 1, cache) + memoizedFibonacci(n - 2, cache); 
  return cache[n];
}

console.log(memoizedFibonacci(5)); // First call, calculates and caches the result
console.log(memoizedFibonacci(5)); // Second call, returns cached value immediately

Explanation:

1. cache Object: A cache object is used to store previously computed results (key-value pairs).

2. Check Cache (if (n in cache)): Before recalculating, the function checks if the result for n already exists in the cache. If it does, the cached value is returned directly.

3. Base Case: For simple cases (n <= 1), the function returns the base value directly.

4. Recursive Calculation and Caching: If the result isn't in the cache, the function calculates it recursively, stores the result in the cache, and then returns the computed value.

Key Points:

• Memoization is most effective for functions with overlapping subproblems (recursive or iterative).

• The cache can be any suitable data structure (object, array) to store results efficiently.