Added top-view

Author: avidLearnerInProgress

top_view_binary_tree.cpp

@@ -0,0 +1,97 @@
+{
+#include <bits/stdc++.h>
+using namespace std;
+/* A binary tree node has data, pointer to left child
+   and a pointer to right child */
+struct Node
+{
+    int data;
+    struct Node* left;
+    struct Node* right;
+    Node(int x){
+        data = x;
+        left = right = NULL;
+    }
+};
+void topView(struct Node *root);
+/* Driver program to test size function*/
+int main()
+{
+  int t;
+  struct Node *child;
+  cin >> t;
+  while (t--)
+  {
+     map<int, Node*> m;
+     int n;
+     cin >> n;
+     struct Node *root = NULL;
+     while (n--)
+     {
+        Node *parent;
+        char lr;
+        int n1, n2;
+        scanf("%d %d %c", &n1, &n2, &lr);
+        if (m.find(n1) == m.end())
+        {
+           parent = new Node(n1);
+           m[n1] = parent;
+           if (root == NULL)
+             root = parent;
+        }
+        else
+           parent = m[n1];
+        child = new Node(n2);
+        if (lr == 'L')
+          parent->left = child;
+        else
+          parent->right = child;
+        m[n2]  = child;
+     }
+     topView(root);
+     cout << endl;
+  }
+  return 0;
+}
+
+}
+/*This is a function problem.You only need to complete the function given below*/
+//Structure of binary tree
+/*struct Node
+struct Node
+{
+    int data;
+    struct Node* left;
+    struct Node* right;
+    
+    Node(int x){
+        data = x;
+        left = right = NULL;
+    }
+};*/
+// function should print the topView of the binary tree
+void topView(struct Node *root)
+{
+    //Your code here
+    
+    map<int, int> m;   //node->data, vertical_dist
+    queue<pair<Node*, int>> q; //node, verticaL_dist
+    q.push({root, 0});
+    while(!q.empty()){
+        pair<Node*, int> top = q.front();
+        Node* c = top.first;
+        int hd = top.second;
+        q.pop();
+        if(m.find(hd) == m.end()){
+            //v.push_back(c->data);
+            m[hd] = c->data; 
+        }
+        if(c->left)
+            q.push({c->left, hd - 1});
+        
+        if(c->right)
+            q.push({c->right, hd + 1});
+    }
+    for(auto i: m)
+        cout<<i.second<<" ";   
+}