Create main.cpp

Author: JawadSher

17 - Binary Tree Data Structure Problems/18 - Top View of Binary Tree/main.cpp

@@ -0,0 +1,44 @@
+class Solution
+{
+    public:
+    //Function to return a list of nodes visible from the top view 
+    //from left to right in Binary Tree.
+    vector<int> topView(Node *root)
+    {
+        vector<int> ans;
+        if(root == NULL) return ans;
+        
+        map<int, int> topNode;
+        queue<pair<Node*, int>> q;
+        
+        q.push({root, 0});
+        
+        while(!q.empty()){
+            pair<Node*, int> temp = q.front();
+            q.pop();
+            
+            Node* frontNode = temp.first;
+            int hd = temp.second;
+            
+            if(topNode.find(hd) == topNode.end()){
+                topNode[hd] = frontNode -> data;
+            }
+            
+            if(frontNode -> left){
+                q.push({frontNode -> left, hd -1});
+            }
+            
+            if(frontNode -> right){
+                q.push({frontNode -> right, hd + 1});
+            }
+            
+        }
+        for(auto i : topNode){
+            ans.push_back(i.second);
+        }
+        
+        
+        return ans;
+    }
+
+};