Added Clone Graph

Author: ignacio-chiazzo

LeetcodeProblems/Clone_Graph.js

@@ -0,0 +1,67 @@
+/*
+Clone Graph
+https://leetcode.com/problems/clone-graph/description/
+
+Given the head of a graph, return a deep copy (clone) of the graph. Each node in the graph contains a label (int) and a list (List[UndirectedGraphNode]) of its neighbors. There is an edge between the given node and each of the nodes in its neighbors.
+
+
+OJ's undirected graph serialization (so you can understand error output):
+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 #.
+
+First node is labeled as 0. Connect node 0 to both nodes 1 and 2.
+Second node is labeled as 1. Connect node 1 to node 2.
+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
+         / \
+         \_/
+Note: The information about the tree serialization is only meant so that you can understand error output if you get a wrong answer. 
+You don't need to understand the serialization to solve the problem.
+*/
+
+/**
+ * Definition for undirected graph.
+ * function UndirectedGraphNode(label) {
+ *     this.label = label;
+ *     this.neighbors = [];   // Array of UndirectedGraphNode
+ * }
+ */
+
+/**
+ * @param {UndirectedGraphNode} graph
+ * @return {UndirectedGraphNode}
+ */
+var cloneGraph = function(graph) {
+  if(!graph)
+      return graph;
+  
+  return dfs(graph, {});
+};
+
+var dfs = function(graph, visited) {
+  if(visited[graph.label]) 
+      return visited[graph.label];
+  
+  var newNode = new UndirectedGraphNode(graph.label);
+  visited[newNode.label] = newNode;
+  
+  for(var i = 0; i < graph.neighbors.length; i++) {
+      const neighbor = dfs(graph.neighbors[i], visited);
+      newNode.neighbors.push(neighbor);
+  }
+  
+  return newNode;
+}