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Problem: Clone Graph

Explore how to create a deep copy of a connected undirected graph in C#. Learn to use breadth-first search and a mapping dictionary to clone nodes and replicate edges, ensuring each node and its neighbors are duplicated correctly.

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)

  • A list of its neighboring nodes (neighbors)

Examples

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Try it yourself!

Implement your solution in the following coding playground.

C#
usercode > Solution.cs
using System;
using System.Collections.Generic;
public class Solution
{
    public Node Clone(Node root)
    {
        // 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 dictionary (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 create ...