Left_view of Binary Search Tree added.

binary_search_tree/Left_View.java

@@ -0,0 +1,96 @@
+package Binarytree;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Scanner;
+
+class Node{
+    int data;
+    Node left;
+    Node right;
+    Node(int element)
+    {
+        this.data = element;
+        this.left = this.right = null;
+    }
+}
+
+class BST{
+    Node root;
+    BST()
+    {
+        root = null;
+    }
+    void addNode(int element)
+    {
+        root = add(root,element);
+    }
+    Node add(Node node, int element)
+    {
+        if(node == null)
+            return new Node(element);
+        if(element<=node.data)
+            node.left = add(node.left,element);
+        else
+        if(element>node.data)
+            node.right = add(node.right,element);
+
+        return node;
+    }
+
+    void inorder(Node root)
+    {
+        if(root == null)
+            return;
+        inorder(root.left);
+        System.out.print(root.data+" ");
+        inorder(root.right);
+    }
+
+        ArrayList<Integer> leftView(Node node)
+        {
+            ArrayList<Integer> al = new ArrayList<>();
+
+            Queue<Node> q = new LinkedList<>();
+            q.add(node);
+            while(!q.isEmpty())
+            {
+                int n = q.size();
+                for(int i=1;i<=n;i++)
+                {
+                    Node temp = q.poll();
+                    if(i==1) {
+                        al.add(temp.data);
+                    }
+                    if(temp.left!=null)
+                        q.add(temp.left);
+                    if(temp.right!=null)
+                        q.add(temp.right);
+
+                }
+            }
+            return al;
+        }
+}
+
+public class Left_View {
+    public static void main(String[] args) {
+        Scanner s = new Scanner(System.in);
+        BST obj = new BST();
+
+        obj.addNode(9);
+        obj.addNode(6);
+        obj.addNode(5);
+        obj.addNode(8);
+        obj.addNode(7);
+        obj.addNode(13);
+        obj.addNode(17);
+        obj.addNode(19);
+        System.out.println("Inorder of entered Tree is: ");
+        obj.inorder(obj.root);
+        ArrayList<Integer> al = new ArrayList<>();
+        al = obj.leftView(obj.root);
+        System.out.println("\nLeft View of this tree is: "+al);
+    }
+}