Added solution

Author: avidLearnerInProgress

populate_next_right_ptr.cpp

@@ -0,0 +1,34 @@
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+    Node* next;
+
+    Node() : val(0), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val) : val(_val), left(NULL), right(NULL), next(NULL) {}
+
+    Node(int _val, Node* _left, Node* _right, Node* _next)
+        : val(_val), left(_left), right(_right), next(_next) {}
+};
+*/
+class Solution {
+public:
+    
+    Node* connect(Node* root) {
+        if(root == NULL) return NULL;
+        
+        if(root->left){ //check if child exists
+            if(root->right) //check if immediate right node of child exists, if yes change the next ptr
+                root->left->next = root->right;
+            if(root->next) //check if neighbour of root exists for subtree, if yes, change the left subtree next ptr to right subtree
+                root->right->next = root->next->left;
+        }
+        connect(root->left);
+        connect(root->right);
+        return root;
+    }
+};