Clone Graph
01 · 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 (val) and a list of its neighbors (neighbors).
class Node {
public int val;
public List<Node> 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.
02 · Examples
adjList = [[2,4],[1,3],[2,4],[1,3]]
[[2,4],[1,3],[2,4],[1,3]]
There are 4 nodes forming a cycle: 1-2-3-4-1. Each node is cloned with its neighbors correctly referencing the new cloned nodes, not the originals.
adjList = [[]]
[[]]
The graph has a single node with val = 1 and no neighbors. The clone is a new node with val = 1 and an empty neighbors list.
adjList = []
[]
The graph is empty (null input), so the output is also null/empty.
03 · Constraints
- 01The number of nodes in the graph is in the range [0, 100].
- 021 <= Node.val <= 100
- 03Node.val is unique for each node.
- 04There are no repeated edges and no self-loops in the graph.
- 05The graph is connected and all nodes can be visited starting from the given node.
04 · Optimal complexity
- Time
- O(V + E)
- Space
- O(V)
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