133. Clone Graph

Dear 丶 2022-02-15 14:21 131阅读 0赞

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 val (int) and a list (List[Node]) of its neighbors.
    
     
    
    Example:
    
    1->2->3->4->1
    
    Input:
    {"$id":"1","neighbors":[{"$id":"2","neighbors":[{"$ref":"1"},{"$id":"3","neighbors":[{"$ref":"2"},{"$id":"4","neighbors":[{"$ref":"3"},{"$ref":"1"}],"val":4}],"val":3}],"val":2},{"$ref":"4"}],"val":1}
    
    Explanation:
    Node 1's value is 1, and it has two neighbors: Node 2 and 4.
    Node 2's value is 2, and it has two neighbors: Node 1 and 3.
    Node 3's value is 3, and it has two neighbors: Node 2 and 4.
    Node 4's value is 4, and it has two neighbors: Node 1 and 3.
     
    
    Note:
    
    The number of nodes will be between 1 and 100.
    The undirected graph is a simple graph, which means no repeated edges and no self-loops in the graph.
    Since the graph is undirected, if node p has node q as neighbor, then node q must have node p as neighbor too.
    You must return the copy of the given node as a reference to the cloned graph.

Node节点定义：

class Node {
        public int val;
        public List<Node> neighbors;
    
        public Node() {}
    
        public Node(int _val,List<Node> _neighbors) {
            val = _val;
            neighbors = _neighbors;
        }
    }

本题可用DFS和BFS两种方法完成。

DFS：

public Node cloneGraph(Node node) {
            Map<Integer, Node> map = new HashMap<>();
            return clone(node, map);
        }
    
        private Node clone(Node node, Map<Integer, Node> map) {
            if(node == null) {
                return null;
            }
            if(map.containsKey(node.val)) {
                return map.get(node.val);
            }
            Node clone = new Node(node.val, new ArrayList<>());
            map.put(node.val, clone);
            for(Node item : node.neighbors) {
                clone.neighbors.add(clone(item, map));
            }
            return clone;
        }

BDS：

public Node cloneGraph(Node node) {
            if(node == null) {
                return null;
            }
            Node clone = new Node(node.val, new ArrayList<>());
            Map<Integer, Node> map = new HashMap<>();
            map.put(node.val, clone);
            Queue<Node> queue = new ArrayDeque<>();
            queue.add(node);
            while(!queue.isEmpty()) {
                Node temp = queue.poll();
                for(Node item : temp.neighbors) {
                    if(!map.containsKey(item.val)) {
                        queue.add(item);
                        Node newNode = new Node(item.val, new ArrayList<>());
                        map.put(item.val, newNode);
                        map.get(temp.val).neighbors.add(newNode);
                    } else {
                        map.get(temp.val).neighbors.add(map.get(item.val));
                    }
                }
            }
            return clone;
        }