How should I practice Number of Connected Components in an Undirected Graph?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Google phone screen problems in FastPrep.

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Number of Connected Components in an Undirected Graph

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Problem statement

You are given an undirected graph with n vertices labeled from 0 to n - 1 and an edge list edges. Return the number of connected components in the graph.

Function

countComponents(n: int, edges: int[][]) → int

Examples

Example 1

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

The components are {0,1,2} and {3,4}.

Example 2

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

Every vertex is connected through one chain.

Example 3

n = 4edges = []return = 4

With no edges, each vertex forms its own component.

Constraints

1 <= n <= 2000.
0 <= edges.length <= 5000.
edges[i].length = 2.
0 <= edges[i][0], edges[i][1] < n.
There are no self-loops or duplicate edges.