Dev Nest Guide
javascriptadvanced10 minutes

Predict the Output of a Complex Recursive and Memoized Function

Analyze the provided JavaScript function that uses recursion, memoization, and bitwise operations to determine its output when called with a specific input.

Challenge prompt

Consider the following JavaScript code snippet. Predict the output when executing `mysteryFunction(10)`. Explain your reasoning about how the recursion and memoization influence the outcome.

Guidance

  • • Trace the recursion flow and understand how memoization caches results to avoid repeated calculations.
  • • Pay attention to bitwise operations and how they alter the function parameters and results.
  • • Focus on how the combination of recursion and bitwise shifts affects the base cases and final returned values.

Hints

  • • Memoization drastically reduces the number of calls by caching results.
  • • Bitwise operations change the value and effectively partition subproblems in recursion.
  • • Consider writing down or using a tree diagram to visualize recursive calls and returns.

Starter code

function mysteryFunction(n, memo = {}) {
  if (n <= 1) return n;
  if (memo[n]) return memo[n];

  const left = mysteryFunction(n >> 1, memo);
  const right = mysteryFunction(n >> 2, memo);
  memo[n] = left + right + (n & 1);

  return memo[n];
}

console.log(mysteryFunction(10));

Expected output

6

Core concepts

recursionmemoizationbitwise operations

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