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60 lines
1.4 KiB
Plaintext
60 lines
1.4 KiB
Plaintext
---
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title: '323. Number of Connected Components in an Undirected Graph'
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description: You have a graph of n nodes. You are given an integer n and an array edges where edges[i] = [ai, bi] indicates that there is an edge between ai and bi in the graph
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icon: dot
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sidebar:
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label: 'Number of Connected Components in an Undirected Graph'
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badge: 'Medium'
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---
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<Badge variant="accent">Depth-First Search</Badge>
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### Example 1:
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- Input: `n = 5, edges = [[0,1],[1,2],[3,4]]`
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- Output: `2`
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### Example 2:
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- Input: `n = 5, edges = [[0,1],[1,2],[2,3],[3,4]]`
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- Output: `1`
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### Constraints:
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- `1 <= n <= 2000`
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- `1 <= edges.length <= 5000`
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- `edges[i]` = [ai, bi]
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- `ai != bi`
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- There are no repeated edges.
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## Solution
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```py
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class Solution:
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def countComponents(self, n: int, edges: list[list[int]]) -> int:
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par = [i for i in range(n + 1)]
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rank = [1] * (n + 1)
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def find(n):
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res = n
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while res != par[res]:
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par[res] = par[par[res]]
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res = par[res]
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return res
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def union(n1, n2):
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p1, p2 = find(n1), find(n2)
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if p1 == p2:
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return 0
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if rank[p1] > rank[p2]:
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par[p2] = p1
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rank[p1] += rank[p2]
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else:
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par[p1] = p2
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rank[p2] += rank[p1]
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return 1
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res = n
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for n1, n2 in edges:
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res -= union(n1, n2)
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return res
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```
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