[LeetCode] 0133. Clone graph

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Medium

Given a reference of a node in a connected undirected graph.

Return a deep copy (clone) of the graph.

Each node in the graph contains a value (int) and a list (List[Node]) of its neighbors.

class Node { public int val; public List neighbors; }

Test case format:

For simplicity, each node's value is the same as the node's index (1-indexed). For example, the first node with val==1, the second node with val==2, and so on. The graph is represented in the test case using an adjacency list.

An adjacency list is a collection of unordered lists used to represent a finite graph. Each list describes the set of neighbors of a node in the graph.

The given node will always be the first node with val=1. You must return the copy of the given node as a reference to the cloned graph.

Example 1:

Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
Output: [[2,4],[1,3],[2,4],[1,3]]
Explanation: There are 4 nodes in the graph. 1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4). 2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3). 3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4). 4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).

Example 2:

Input: adjList = [[]]
Output: [[]]
Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors.

Example 3:

Input: adjList = []
Output: []
Explanation: This an empty graph, it does not have any nodes.

Constraints:

The number of nodes in the graph is in the range [0, 100].
1 <= Node.val <= 100
Node.val is unique for each node.
There are no repeated edges and no self-loops in the graph.
The Graph is connected and all nodes can be visited starting from the given node.

Table of contents

Python

				
					# Definition for a Node. class Node: def __init__(self, val=0, neighbors=None): self.val = val self.neighbors = neighbors if neighbors is not None else [] class Solution: def __init__(self): self.visited = {} def cloneGraph(self, node: 'Node') -> 'Node': if not node: return node if node in self.visited: return self.visited[node] clone_node = Node(node.val , []) self.visited[node] = clone_node if node.neighbors: clone_node.neighbors = [self.cloneGraph(n) for n in node.neighbors] return clone_node

Python

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