Merge pull request #28 from aryandeelwal/aryan-branch-coding

Add a Leetcode medium level question - Clone Graph in C++

Author: vaibhavagarwal47

LeetCode/clone_graph.cpp

@@ -0,0 +1,59 @@
+# Question Link - https://leetcode.com/problems/clone-graph/
+/* Input:
+[[2,4],[1,3],[2,4],[1,3]]
+*/
+/* Output:
+[[2,4],[1,3],[2,4],[1,3]]
+*/
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    vector<Node*> neighbors;
+    Node() {
+        val = 0;
+        neighbors = vector<Node*>();
+    }
+    Node(int _val) {
+        val = _val;
+        neighbors = vector<Node*>();
+    }
+    Node(int _val, vector<Node*> _neighbors) {
+        val = _val;
+        neighbors = _neighbors;
+    }
+};
+*/
+class Solution {
+private:
+    Node* dfs(Node* curr, unordered_map<Node*,Node*>& mp)
+    {
+        vector<Node*> neighbor;
+        Node* clone = new Node(curr->val);
+        mp[curr] = clone;
+         for(auto it : curr->neighbors)
+         {
+             if(mp.find(it) != mp.end()) {       //already cloned and stored in map
+                 neighbor.push_back(mp[it]); 
+             }
+             else {
+                 neighbor.push_back(dfs(it,mp));
+             }
+         }
+        clone->neighbors = neighbor;
+        return clone;
+    }
+public:
+    Node* cloneGraph(Node* node) {
+        unordered_map<Node*,Node*> mp;
+        if(node == NULL) 
+            return NULL;
+        if(node->neighbors.size() == 0)
+        {
+            Node* clone = new Node(node->val);
+            return clone;
+        }
+        return dfs(node,mp);
+    }
+};