LeetCode-Microsoft-Clone Graph

Posted 2020-11-01 IncredibleThings

Clone an undirected graph. Each node in the graph contains a label and a list of its neighbors.

OJ\'s undirected graph serialization:

Nodes are labeled uniquely.

We use # as a separator for each node, and , as a separator for node label and each neighbor of the node.

 

As an example, consider the serialized graph {0,1,2#1,2#2,2}.

The graph has a total of three nodes, and therefore contains three parts as separated by #.

1. First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
2. Second node is labeled as 1. Connect node 1 to node 2.
3. Third node is labeled as 2. Connect node 2 to node 2 (itself), thus forming a self-cycle.

 

Visually, the graph looks like the following:

       1
      / \\
     /   \\
    0 --- 2
         / \\
         \\_/


Reference: https://www.cnblogs.com/springfor/p/3874591.html

/**
 * Definition for undirected graph.
 * class UndirectedGraphNode {
 *     int label;
 *     List<UndirectedGraphNode> neighbors;
 *     UndirectedGraphNode(int x) { label = x; neighbors = new ArrayList<UndirectedGraphNode>(); }
 * };
 */
public class Solution {
    public UndirectedGraphNode cloneGraph(UndirectedGraphNode node) {
        if(node == null){
            return null;
        }
        //queue
        Queue<UndirectedGraphNode> queue = new LinkedList<>();
        //map
        Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();
        UndirectedGraphNode head = new UndirectedGraphNode(node.label);
        
        map.put(node, head);
        queue.add(node);
        while(!queue.isEmpty()){
            UndirectedGraphNode curnode = queue.poll();
            //check each neighbor
            for(UndirectedGraphNode aneighbor: curnode.neighbors){
                //if not visited,then add to queue
                if(!map.containsKey(aneighbor)){
                    queue.add(aneighbor);
                    UndirectedGraphNode newneighbor = new UndirectedGraphNode(aneighbor.label);
                    map.put(aneighbor, newneighbor);
                }
                map.get(curnode).neighbors.add(map.get(aneighbor));
            }
        }
        return head;
    }
}

 BFS:

/*
// Definition for a Node.
class Node {
    public int val;
    public List<Node> neighbors;
    public Node() {
        val = 0;
        neighbors = new ArrayList<Node>();
    }
    public Node(int _val) {
        val = _val;
        neighbors = new ArrayList<Node>();
    }
    public Node(int _val, ArrayList<Node> _neighbors) {
        val = _val;
        neighbors = _neighbors;
    }
}
*/

class Solution {
    public Node cloneGraph(Node node) {
        if (node == null) {
            return null;
        }
        
        Node head = new Node(node.val);
        Map<Integer, Node> toBeVisit = new HashMap<>();
        toBeVisit.put(head.val, head);
        Queue<Node> queue = new LinkedList<>();
        queue.add(node);
        while(!queue.isEmpty()) {
            Node aNode = queue.remove();
            for (Node nbh : aNode.neighbors) {
                if (!toBeVisit.containsKey(nbh.val)) {
                    Node nbhNode = new Node(nbh.val);
                    toBeVisit.put(nbhNode.val, nbhNode);
                    queue.add(nbh);
                }
                toBeVisit.get(anode.val).neighbors.add(toBeVisit.get(nbh.val));
            }
        }
        return head;
    }
}