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UBER | Online Assessment

Round 1

Questions:

Problem 1: Valid String Check

Difficulty: Easy

Description: Given a string, check if it is valid or not. A valid string must:

Testcases: Valid strings: 771, 777, 123777
Invalid strings: 12345, 71, 171, 70

Candidate's Approach

I implemented a simple approach, doing as asked in the description for each string.

Interviewer's Feedback

No feedback provided.


Problem 2: Command Frequency Counter

Difficulty: Easy

Description: You are given an array of commands. There are only three possible commands: cmd1, cmd2, and cmd3. Your task is to return an array of size 3 that contains the frequency of each command in the input array, in the order [frequency of cmd1, frequency of cmd2, frequency of cmd3].

Also, any element in the form of ! refers to the same command that was present at the position in the input array. Note that indexing starts from 1 (not 0).

Input:

[cmd1, cmd2, cmd3, !1, !2, cmd3, cmd1]

Output:

[3, 2, 2]

At index 4 (!1), the command is the same as the command at index 1 (cmd1).
At index 5 (!2), the command is the same as the command at index 2 (cmd2).

Candidate's Approach

I solved it in one pass with no extra space.

Interviewer's Feedback

No feedback provided.


Problem 3: Regional Maximum Finder

Difficulty: Medium or maybe Hard

Description: You are given a 2D array. Your task is to find the regional maxima in the array and return a 2D array of size (X * 2) where each row contains the position [i, j] of a regional maximum.

Definition of Regional Maximum: A cell (i, j) is considered a regional maximum if:

Definition of Region: For a cell (i, j) with value cell:

Input:

[ [3, 0, 1], [2, 0, 0], [0, 0, 0], ]

Output:

[[0, 0], [0, 2]]

The dimensions of the array were relatively small, like 100 * 100, so performance constraints were manageable.

Candidate's Approach

I solved it with worse time-complexity (4 nested loops) same as what comes to mind at first glance, not sure how to optimise. Would love to know your thoughts.

Interviewer's Feedback

No feedback provided.


Problem 4: Sliding Window Problem

Difficulty: Leetcode says Hard

The fourth problem was based on this LeetCode question:
Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit

The problem statement was phrased differently, but the solution required implementing the exact same logic as this LeetCode problem.

Candidate's Approach

I gave the most optimal solution; you can check out the discussion tab of the problem.

Interviewer's Feedback

No feedback provided.