Problem - Number of Connected Components

Given $n$ nodes labeled from $0$ to $n-1$ and a list of undirected edges, count the number of connected components in the graph.

Example: $n = 5$, edges $= [[0,1], [1,2], [3,4]]$ returns $2$ (components {0,1,2} and {3,4}). You're solving the canonical Union-Find problem.

Union all edges, then count distinct roots. Constraints: $n$ from $1$ to $2000$, edges from $0$ to $5000$.