Flatten a deeply nested array of numbers and return most frequent number with its count

Q: Flatten a deeply nested array of numbers and return most frequent number with its count

// Find the Most Frequent Element and its count from the following Array const arr = [12, [23, [31, 23], 5], 23, 5, 8, [2, 5, 6, 8], 5]; let flatArray = arr.flat(2); let output = {}; let maxCount = 0; function findMostFreq(arr) { for (let i = 0; i < arr.length; i++) { if (output[arr[i]]) { output[arr[i]]++; } else { output[arr[i]] = 1; } if (maxCount < output[arr[i]]) { maxCount = output[arr[i]]; } } return maxCount; } console.log(findMostFreq(flatArray));

Difficulty: 5/10

recursion, hash maps, time complexity

javascript

Scenario Questions

0-2 years experience

1We have a utility function that processes user-submitted survey data, which sometimes comes in as nested arrays of scores like `[1, [2, [2, 3]], 1]`. How would you write a function to flatten this data and find the most common score and how many times it appeared?
2Imagine you wrote a recursive function to flatten this array, but during testing with a deeply nested array (like 10,000 levels deep), the browser tab crashed with a 'Maximum call stack size exceeded' error. What is happening here, and how would you modify your code to prevent it?

Follow-up Questions

How would you modify your solution to handle ties where multiple numbers have the same maximum frequency?
If the input array is extremely deep (e.g., 20,000 levels), how do you prevent a stack overflow in JavaScript?
What is the space complexity of your solution, and can we optimize it if we are memory-constrained?