Merge pull request #186 from favjava/main

Added TopView of Tree

C++/Algorithms/TopViewOfTree.cpp

@@ -0,0 +1,75 @@
+#include<bits/stdc++.h>
+using namespace std;
+// structure of node
+struct Node
+{
+    Node *left; //left pointer
+    Node *right;//right pointer
+    int data;
+    int line;//line denotes the line number 0 for root 
+    //left side of root starts with negative line numbers
+    //right side of root starts with positive line numbers
+};
+//creation of new Node
+Node* newNode(int data)
+{
+    Node* node = new Node();
+    node->left = node->right = NULL;//assign NUll to both left and right pointer
+    node->data = data;//assign the value to the data field
+    return node;//return the node.
+}
+// this function identifies the nodes present at the top 
+void topView(Node *root)
+{
+    vector<int>ans;// vector to store the final view nodes
+
+    if(root == NULL)return;
+    // map to store the node with line number
+    map<int,int> mp;
+    //queue to store the Node and line number
+    queue<pair<Node*,int>>q;
+    q.push({root,0});//push the very first Node i.e. root.
+    //traverse while the queue is not empty
+    while(!q.empty()){
+        auto it = q.front();//pointer to store the front of queue
+        q.pop();// then pop the element
+        // store the node and line in the  respective variables
+        Node* node = it.first;
+        int line = it.second;
+
+        //if line not present in the map 
+        //then add the line number with respective node.
+        if(mp.find(line)==mp.end())
+        {
+            mp[line] = node->data;
+        }
+
+        //if line present the traverse the other nodes.
+
+        //if left node present push the left node and decrement the line number
+        if(node->left != NULL)q.push({node->left ,line-1});
+        // if ritgh node present push the right node and increment the line number.
+        if(node->right != NULL)q.push({node->right,line+1});
+
+    }
+    // display the value of map which contains the top view 
+    cout<<"Top View of Tree is: ";
+    for(auto i:mp)
+    {
+        cout<<i.second<<" ";
+    }
+}
+int main()
+{
+    //create a tree with root and its childrens
+    Node* root = newNode(1);
+    root->left = newNode(2);
+    root->right = newNode(3);
+    root->left->left = newNode(4);
+    root->left->right= newNode(5);
+    root->left->right->left = newNode(6);
+    root->right->right= newNode(7);
+    //call the function to calculate the top view.
+    topView(root);
+    return 0;
+}