Problem Description

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.

Examples

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.

解析

題目給定一個整數 n 代表有 0 到 n-1 vertex

還有一個 edges 矩陣用來表示有相連的 edge

要求寫一個演算法來計算有相連的區塊個數

作法1:

透過 edges 可以推算出 adjacency list

然後針對 adjacency list 做 DFS 走訪所有相連的區塊