MEDIUM NC#81 Blind #27 Graphs / DFS
133. Clone Graph
📖 Problem
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. 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.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •Recursive stack flow
- •Cycle prevention
- •Post-order reasoning
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply DFS reasoning pattern
💡 Approach
- → Use hash map to track cloned nodes
- → Use DFS to traverse graph and create clones
- → When encountering already cloned node, return from map
- → Time: O(V + E), Space: O(V + E)
🛠️ Hints & Pitfalls
Hints
- •Use hash map to track cloned nodes
- •Use DFS to traverse graph and create clones
- •When encountering already cloned node, return from map
Common Pitfalls
- •Time: O(V + E), Space: O(V + E)
🧪 Test Cases
Test Case 1
Not run Input:
dfs(curr: GraphNode | null); Expected:
Computed from hidden reference Test Case 2
Not run Input:
dfs(neighbor); Expected:
Computed from hidden reference Test Case 3
Not run Input:
dfs(node); Expected:
Computed from hidden reference 📝 Code Editor
📤 Output