[LeetCode] 133. Clone Graph - 문제풀이

Description

연결된 무방향 그래프에서 노드의 참조가 주어집니다. 그래프의 전체 복사본(클론)을 반환합니다.

그래프의 각 노드에는 인접 노드의 값(int)과 목록(List[Node])이 포함됩니다.

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.

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.

Example 1:

Input: adjList = [[2,4],[1,3],[2,4],[1,3]]
Output: [[2,4],[1,3],[2,4],[1,3]]
Explanation: There are 4 nodes in the graph.
1st node (val = 1)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
2nd node (val = 2)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).
3rd node (val = 3)'s neighbors are 2nd node (val = 2) and 4th node (val = 4).
4th node (val = 4)'s neighbors are 1st node (val = 1) and 3rd node (val = 3).

Example 2:

Input: adjList = [[]]
Output: [[]]
Explanation: Note that the input contains one empty list. The graph consists of only one node with val = 1 and it does not have any neighbors.

Example 3:

Input: adjList = []
Output: []
Explanation: This an empty graph, it does not have any nodes.

Constraints:

• The number of nodes in the graph is in the range [0, 100].
• 1 <= Node.val <= 100
• Node.val is unique for each node.
• There are no repeated edges and no self-loops in the graph.
• The Graph is connected and all nodes can be visited starting from the given node.

public class UndirectedGraphNode {
    public int val;
    public List<UndirectedGraphNode> neighbors;
    public UndirectedGraphNode() {
        val = 0;
        neighbors = new ArrayList<UndirectedGraphNode>();
    }
    public UndirectedGraphNode(int _val) {
        val = _val;
        neighbors = new ArrayList<UndirectedGraphNode>();
    }
    public UndirectedGraphNode(int _val, ArrayList<UndirectedGraphNode> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
}

Solution 1. BFS

public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
    if(node == null) return null;
    Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();
    map.put(node, new UndirectedGraphNode(node.val));
    Queue<UndirectedGraphNode> q = new LinkedList<>();
    q.offer(node);
    while(!q.isEmpty()){
        UndirectedGraphNode cur = q.poll();
        for(UndirectedGraphNode neighbor : cur.neighbors){
            if(!map.containsKey(neighbor)){
                map.put(neighbor, new UndirectedGraphNode(neighbor.val));
                q.offer(neighbor);
            }
            map.get(cur).neighbors.add(map.get(neighbor));
        }

    }
    return map.get(node);
}

너비우선탐색(BFS)를 통해 방문하지 않았던 인접노드들을 방문하며 새로운 노드들을 생성합니다.

Reference

Clone Graph - LeetCode