Number of Connected Components in an Undirected Graph

Given n nodes labeled from 0 to n – 1 and a list of undirected edges (each edge is a pair of nodes), write a function to find the number of connected components in an undirected graph.

Example 1:

     0              3

     |                |

     1 — 2      4

Given n = 5 and edges = [[0, 1], [1, 2], [3, 4]], return 2.

Example 2:

     0              4 

     |                |

     1 — 2 — 3

Given n = 5 and edges = [[0, 1], [1, 2], [2, 3], [3, 4]], return 1.

 Note:

You can assume that no duplicate edges will appear in edges. Since all edges are undirected, [0, 1] is the same as [1, 0] and thus will not appear together in edges.

 

We can solve this problem using Union find method. 

Here are some good articles to learn union find data structure:

https://www.cs.princeton.edu/~rs/AlgsDS07/01UnionFind.pdf

http://algs4.cs.princeton.edu/15uf/