Clone Graph

10 min read

Input:adjList = [[2,4],[1,3],[2,4],[1,3]]

Output:[[2,4],[1,3],[2,4],[1,3]]

Explain:

Return a deep copy of the graph.

Given a reference of a node in a connected undirected graph.
Return a deep copy (clone).

Deep Copy: New nodes, new edges. You cannot return references to the original nodes.

We need to traverse the entire graph and create a copy of each node exactly once.

Key Tool: HashMap<OldNode, NewNode>.

Check Map: If we already cloned this node, return the NewNode from the map (handles cycles).
Create: If not, create NewNode(val) and add to map.
Recurse: Iterate through OldNode.neighbors. For each neighbor, recursively call clone(neighbor) and add the result to NewNode.neighbors.

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Custom Input

Mapping Old Nodes to New Nodes to Avoid Cycles.

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