Software Engineer · Online Assessment · Coding

IBM — Software Engineer

Level: Junior-Level

Round: Online Assessment · Type: Coding · Difficulty: 6/10 · Duration: 60 min · Interviewer: Unfriendly

Topics: Arrays, Intervals, Graph Theory, Connectivity, Union Find

Location: San Francisco Bay Area

Interview date: 2025-09-21

Summary

I completed an online assessment with two questions on HackerRank.

Details

The online assessment consisted of two coding problems:

Question 1: Maximum Concurrent Processes

Problem Description: Given a set of logs, each containing a start and end time (both inclusive), representing the active period of a process. Find the maximum number of processes running concurrently at any given time.

Input: A 2D array where each element is [start, end], representing a process's active interval. Output: An integer representing the maximum number of concurrent processes.

Examples:

1. Input: [[1, 3], [2, 4], [3, 6]]
   • At time 3, three processes are active.
   • Output: 3
2. Input: [[2, 6], [1, 2], [3, 5]]
   • The maximum number of concurrent processes is 2.
   • Output: 2

Question 2: Minimum Link Redistribution

Problem Description: You manage link_nodes code repositories, numbered from 1 to link_nodes. Some repositories are already synchronized through bidirectional links. Repositories A and B are considered synchronized if they are connected directly or indirectly.

You can redistribute existing links by deleting a link and connecting it between any two repositories. The goal is to make all repositories belong to the same synchronized system.

Input:

• link_nodes: The number of nodes.
• link_from[]: An array of link start points.
• link_to[]: An array of link end points.

Output: An integer representing the minimum number of links that need to be redistributed. Return -1 if it's impossible to connect all repositories.

Critical Condition:

• If the number of links is less than link_nodes - 1, it's impossible to connect all nodes → Output -1.
• Otherwise, the answer is "number of connected components - 1".

Examples:

1. Input:
   • link_nodes = 4
   • link_from = [1, 1, 3]
   • link_to = [2, 3, 2]
   • Initial connected components = 2 ({1,2,3}, {4})
   • Needs to redistribute 1 edge → Output 1
2. Input:
   • link_nodes = 4
   • link_from = [1, 2]
   • link_to = [3, 4]
   • Number of links = 2 < 4-1 → Cannot connect → Output -1