Solve frequency and tree-completeness problems

Q: Solve frequency and tree-completeness problems

These two problems evaluate competency in frequency counting and selection algorithms for identifying top-k elements and in binary tree structure analysis and traversal for checking completeness, belonging to the Coding & Algorithms domain and the broader data structures and algorithms category.

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Question

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Problem A: Return the k most frequent values

You are given an integer array nums and an integer k.

Task: Return the k distinct values that occur most frequently in nums.

Input

nums : list of integers (length n )
k : integer, 1 <= k <= (# of distinct values in nums)

Output

A list of k integers: the values with highest frequency.

Notes / Constraints

If multiple answers are possible due to ties, any valid order is acceptable.
Aim for better than O(n log n) if possible.

Problem B: Check whether a binary tree is complete

You are given the root of a binary tree.

A binary tree is complete if:

Every level except possibly the last is completely filled, and
All nodes in the last level are as far left as possible.

Task: Return true if the tree is complete; otherwise return false.

Input

root : root node of a binary tree (each node has val , left , right )

Output

Boolean: whether the tree is complete.

Constraints

Up to ~ 10^5 nodes.

Solve frequency and tree-completeness problems

Quick Overview

Problem A: Return the k most frequent values

Problem B: Check whether a binary tree is complete

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