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Learn Data Structures and Algorithms in Go

Problem: Clone Graph

Understand how to clone a connected, undirected graph by implementing a breadth-first search in Go. Learn to use a hash map to avoid revisiting nodes and correctly replicate neighbor links. This lesson helps you master graph cloning techniques, improving your grasp of graph traversal and data structure manipulation.

We'll cover the following...

Statement

You are given a reference to a node in a connected, undirected graph. Your task is to return a deep copy (clone) of the entire graph.

Each node in the graph contains:

  • An integer value (data)

  • An array of its neighboring nodes (neighbors)

Examples

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Try it yourself!

Implement your solution in the following coding playground.

Go
usercode > CloneGraph.go
package main
func clone(root *Node) *Node {
	// Replace this placeholder return statement with your code
	return root
}
Clone Graph

Solution

The core idea behind cloning a connected, undirected graph is to traverse the original graph using breadth-first search (BFS) while simultaneously building a copy of each node and replicating the neighbor relationships. We use a hash map (cloneMap) that maps each original node to its corresponding cloned node. This serves two purposes: it tracks which nodes have already been visited (preventing infinite loops in the undirected graph) and provides constant-time access to the cloned counterpart of any original node when wiring up neighbor lists. Starting from the given node, we explore level by level. For every neighbor encountered, we either ...