Number of Connected Components in an Undirected Graph

You are given an integer `n` representing the number of nodes in an undirected graph, labeled from `0` to `n - 1`. You are also given a 2D array `edges`, where each `edges[i] = [ai, bi]` indicates that there is an undirected edge between nodes `ai` and `bi`. Return *the number of connected components* in the graph. **Constraints:** - `1 <= n <= 2000` - `0 <= edges.length <= n * (n - 1) / 2` - `edges[i].length == 2` - `0 <= ai, bi < n` - `ai != bi` - There are no repeated edges.