# My Accepted solution Iterative

• ``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
//1. LookUp table to store parent and child,
// lookUp(childNode, parentNode)
Map<TreeNode,TreeNode> lookUp = new HashMap<>();
//2. Result will be store in the following list
List<String> res = new ArrayList<>();
//3. StringBuilder to build a result on the fly
StringBuilder sb = new StringBuilder();
public List<String> binaryTreePaths(TreeNode root) {
//1. If root is null, return an empty collection
if(root == null)    return res;
//2. Iterative preorder traversal - stack instantiation
Deque<TreeNode> stack = new ArrayDeque<>();
//2.a push root and mark parent of root as null in map
stack.push(root);
lookUp.put(root,null);
//2.b start preoder traversal
while(!stack.isEmpty()){
root = stack.pop();
//2.c If children are null then the node is leaf, call method to prepare result
if(root.left == null && root.right == null) {
}
//2.d  Right node is pushed, as we need to print result of left node first
// also map the child to parent
if(root.right != null) {
stack.push(root.right);
lookUp.put(root.right,root);
}
//2.e Left node is pushed and mapped child to parent
if(root.left != null){
stack.push(root.left);
lookUp.put(root.left,root);
}

}
return res;
}
// Method to create an item for the collection
// Temporary stack to store the result
Deque<TreeNode> temp_Stack = new ArrayDeque<>();
// load the stack by looking up parents
while(root != null){
temp_Stack.push(root);
root = lookUp.get(root);
}
// unload the stack and prepare the result using stringBuilder
while(!temp_Stack.isEmpty()){
root = temp_Stack.pop();
sb = temp_Stack.isEmpty() ? sb.append(root.val) :sb.append(root.val).append("->");
}
// Add the prepared item into collection