Java-DSA/a_156_Top_Bottom_View.java at main · ambresh20/Java-DSA · GitHub

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import java.util.* ;

public class a_156_Top_Bottom_View {

    static class Node{
        int data ;
        Node left , right ;

        Node(int data ) {
            this.data = data ;
            this.left = null ;
            this.right = null ;
        }
    }

    static class Info{
        Node node ;
        int hd ;

        public Info(Node node, int hd){
            this.hd = hd ;
            this.node = node ;
        }
    }

    public static void topView(Node root) {
        // Level Order traversal
        Queue<Info> q = new LinkedList<>() ;
        HashMap<Integer, Node> map = new HashMap<>() ;

        int min = 0, max = 0 ;
        q.add(new Info(root, 0) ) ;
        q.add(null) ;

        while(!q.isEmpty()){
            Info curr = q.remove() ;

            if(curr == null){
                if(q.isEmpty()){
                    break ;
                }
                else{
                    q.add(null) ;
                }
            }
            else{
                if(!map.containsKey(curr.hd)) {     // first time my hd is occuring
                    map.put(curr.hd, curr.node) ;
                }

                if(curr.node.left != null){
                    q.add( new Info(curr.node.left, curr.hd - 1 ) )   ;
                    min = Math.min(min, curr.hd - 1 )  ;
                }

                if(curr.node.right != null){
                    q.add( new Info(curr.node.right, curr.hd + 1 ) )   ;
                    max = Math.max(max, curr.hd + 1 )  ;
                }
            }

        }

        for(int i=min ; i<=max ; i++){
            System.out.print(map.get(i).data +" ");
        }
          System.out.println();

    }

    public static void bottomView (Node root){
         // Level Order traversal
         Queue<Info> q = new LinkedList<>() ;
         HashMap<Integer, Node> map = new HashMap<>() ;

         int min = 0, max = 0 ;
         q.add(new Info(root, 0) ) ;
         q.add(null) ;

         while(!q.isEmpty()){
            Info curr = q.remove() ;

            if(curr == null){
                if(q.isEmpty()){
                    break ;
                }
                else{
                    q.add(null) ;
                }
            }
            else{
                 // if values are duplicates them key are not change , but values changes
                    map.put(curr.hd, curr.node) ;

                if(curr.node.left != null){
                    q.add( new Info(curr.node.left, curr.hd - 1 ) )   ;
                    min = Math.min(min, curr.hd - 1 )  ;
                }

                if(curr.node.right != null){
                    q.add( new Info(curr.node.right, curr.hd + 1 ) )   ;
                    max = Math.max(max, curr.hd + 1 )  ;
                }
            }
        }


        for(int i=min ; i<=max ; i++){
            System.out.print(map.get(i).data +" ");
        }
          System.out.println();

    }

    public static void main(String[] args) {

          /*
                        1
                      /   \
                     2     3
                    / \   / \
                   4   5 6   7

         */

         Node root = new Node(1) ;
         root.left = new Node(2) ;
         root.right = new Node(3) ;
         root.left.left = new Node(4) ;
         root.left.right = new Node(5) ;
         root.right.left = new Node(6) ;
         root.right.right = new Node(7) ;

        bottomView(root);


    }
}