Create top_view of binary tree.cpp

top_view of binary tree.cpp

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+//Top view in binary tree----set of nodes visible when the tree is viewed from the top
+
+//          1
+//         /  \
+//        2     3
+//       / \   /  \
+//      4   5  6   7
+//   here top view is  4 2 1 3 7
+
+// iterative approach  -- using queue
+#include <bits/stdc++.h>
+using namespace std;
+typedef long long int ll;
+
+struct node{
+    int data;
+    struct node*left;
+    struct node*right;
+// constructor
+    node(int val){
+        data=val;
+        left=right=NULL;
+    }
+};
+
+void topview(struct node*root){
+    queue<pair<struct node*, int>>q;
+    map<int,int>mp;
+    q.push({root,0});
+    while(!q.empty()){
+struct node*curr=q.front().first;
+int dist=q.front().second;
+q.pop();
+if(mp.count(dist)==0){ 
+
+    mp[dist]=curr->data;
+}
+if(curr->left!=NULL){
+    q.push({curr->left,dist-1});
+}
+
+if(curr->right!=NULL){
+    q.push({curr->right,dist+1});
+}
+    }
+
+for(auto i:mp){
+    cout<<i.second<<" ";
+}
+
+}
+    int main() 
+{
+ struct node*root= new node(1);
+ root->left= new node(2);
+ root->right=new node(7);
+ root->left->left=new node(3);
+ root->left->right= new node(4);
+ root->left->right->left= new node(5);
+ root->left->right->right= new node(6);
+
+ topview(root);
+
+return 0;
+}