Union find: merge dynamic connectivity groups efficiently

Union find: Given n nodes and undirected connections, return the number of connected groups after applying every connection.

Input: A JSON object { "n": number, "connections": [number, number][] }.

Output: A JSON integer group count.

Constraints:

0 <= n <= 100000
Every endpoint is in 0..n-1
Repeated and self connections do not change the answer

Read one JSON value from stdin and print exactly one JSON-serialized answer to stdout with no extra text.

Difficulty: EASY. Variant: 7. Expect follow-up questions about complexity, edge cases, and alternative approaches.

Practice context

This coding (algo) exercise trains prompt interpretation, explicit assumptions, a concrete response, and a concise explanation of the decisions made. It is marked easy difficulty.

The signed-in workspace provides the tools required by the round, such as recording, code execution, diagrams, structu

What this task practices

This coding (algo) exercise trains the same sequence expected in an interview: understand the prompt, make assumptions explicit, produce a concrete answer, and explain the decisions behind it. The task is marked easy difficulty. The private workspace adds the tools required by this round, such as recording, code execution, diagrams, evidence panels, or structured notes. It also preserves the attempt so later feedback can be compared with previous work. Evaluation is based on task-specific criteria and the candidate seniority selected in the preparation path. Public pages never expose the reference solution, hidden tests, evaluator instructions, or another candidate’s work.