Boundary_of_Binary_Tree.java

// Indian Army setup some military-camps, sitauted at random places at LAC in Galwan.
// There exist a main base camp connected with other base camps as follows:
// Each military-camp is connected with atmost two other military-camps.
// Each military-camp will be identified with an unique ID,(an integer).

// To safeguard all the military-camps, Govt of India planned to setup protective 
// S.H.I.E.L.D. Govt of India ask your help to build the S.H.I.E.L.D that should 
// enclose all the militar-camps.

// You are given the IDs of the military-camps as binary tree. 
// Your task is to find and return the military camp IDs, those are on the edge of 
// the S.H.I.E.L.D in anti-clockwise order.

// Implement the class Solution:
//    1. public List<Integer> compoundWall(BinaryTreeNode root): returns a list.
  

// NOTE:
// '-1' in the input IDs indicates no military-camp (NULL).


// Input Format:
// -------------
// space separated integers, military-camp IDs.

// Output Format:
// --------------
// Print all the military-camp IDs, which are at the edge of S.H.I.E.L.D.


// Sample Input-1:
// ---------------
// 5 2 4 7 9 8 1

// Sample Output-1:
// ----------------
// [5, 2, 7, 9, 8, 1, 4]


// Sample Input-2:
// ---------------
// 11 2 13 4 25 6 -1 -1 -1 7 18 9 10

// Sample Output-2:
// ----------------
// [11, 2, 4, 7, 18, 9, 10, 6, 13]





import java.util.*;
/*
//TreeNode Structure for Your Reference..

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

*/

class Solution {
   static List<Integer> lst=new ArrayList<>();
   static List<Integer> temp=new ArrayList<>();
   
    public List<Integer> compoundWall(Node root) {
        // Implement Your Code here..
        lst.add(root.data);
        printleft(root.left);
        printleaves(root);
        printright(root.right);
        for(int i=temp.size()-1;i>=0;i--){
            lst.add(temp.get(i));
        }
        return lst;
    }
    public static void printleft(Node root){
        if(root==null){
            return;
        }
        if(root.left==null && root.right==null){
            return;
        }
        lst.add(root.data);
        if(root.left!=null){
            printleft(root.left);
        }
        else if(root.right!=null){
            printleft(root.right);
        }
    }
    public static void printright(Node root){
        if(root==null){
            return;
        }
        if(root.left==null && root.right==null){
            return;
        }
        temp.add(root.data);
        if(root.right!=null){
            printright(root.right);
        }
        else if(root.left!=null){
            printright(root.left);
        }
    }
    public static void printleaves(Node root){
        if(root==null){
            return;
        }
        if(root.left==null && root.right==null){
          lst.add(root.data); 
        }
        printleaves(root.left);
        printleaves(root.right);
    }
}