Number of Connected Components in an Undirected Graph

You have a graph of n nodes labeled from 0 to n - 1. Given an integer n and a list of edges where edges[i] = [a_i, b_i] indicates an undirected edge between node a_i and node b_i, return the number of connected components in the graph.

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Example 1

0 --- 1 --- 2    3 --- 4

Input: n = 5, edges = [[0, 1], [1, 2], [3, 4]]
Output: 2
Explanation: Nodes 0, 1, 2 form one component. Nodes 3, 4 form a second.

Example 2

0 --- 1 --- 2 --- 3 --- 4

Input: n = 5, edges = [[0, 1], [1, 2], [2, 3], [3, 4]]
Output: 1
Explanation: All five nodes are connected in a single chain.

Example 3

Input: n = 5, edges = []
Output: 5
Explanation: No edges means every node is its own isolated component.

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Constraints

• 1 <= n <= 2000
• 0 <= edges.length <= 5000
• edges[i].length == 2
• 0 <= a_i, b_i < n
• a_i != b_i
• No repeated edges