Most Frequent Element in List | Dataford Interview Questions

JioCinema analytics receives a non-empty list of integer event codes from a user session. Write a function that returns the most frequent event code. If multiple codes have the same highest frequency, return the one that appears first in the list.

You should use an algorithm that runs in linear time. Do not modify the input list.

Formal Specification

Implement most_frequent_element(nums).

Input: nums, a non-empty list of integers.
Output: The integer occurring most frequently in nums. If frequencies tie, return the tied integer with the lowest first-occurrence index.

Constraints

1 <= len(nums) <= 100000
-10^9 <= nums[i] <= 10^9
nums contains at least one element
The input list must remain unchanged

Function Signature

def most_frequent_element(nums):

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