133. Clone Graph

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
         / \
         \_/

Solution

(1) Java

/**
 * 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<UndirectedGraphNode> q = new LinkedList<>();
        Map<UndirectedGraphNode, UndirectedGraphNode> map = new HashMap<>();
        UndirectedGraphNode cnode = new UndirectedGraphNode(node.label);
        map.put(node, cnode);
        q.offer(node);
        while (q.size() > 0) {
            UndirectedGraphNode opnode = q.poll();
            List<UndirectedGraphNode> neighbors = opnode.neighbors;
            for (UndirectedGraphNode pnode : neighbors) {
                if (!map.containsKey(pnode)) {
                    UndirectedGraphNode pcnode = new UndirectedGraphNode(pnode.label);
                    map.put(pnode, pcnode);
                    q.offer(pnode);
                } 
                map.get(opnode).neighbors.add(map.get(pnode));
            }
        }
        return cnode;
    }
}

(2) Python

# Definition for a undirected graph node
# class UndirectedGraphNode:
#     def __init__(self, x):
#         self.label = x
#         self.neighbors = []

class Solution:
    # @param node, a undirected graph node
    # @return a undirected graph node
    def cloneGraph(self, node):

        def clone(pnode):
            if not pnode:
                return None
            if pnode in cache:
                return cache[pnode]
            pcnode = UndirectedGraphNode(pnode.label)
            cache[pnode] = pcnode
            for ppcode in pnode.neighbors:               
                cache[pnode].neighbors.append(clone(ppcode))
            return pcnode

        cache = {}
        return clone(node)

(3) Scala