Binary Tree Traversal

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Binary Tree Preorder Traversal

public class Solution {    public ArrayList<Integer> preorderTraversal(TreeNode root) {        ArrayList<Integer> res = new ArrayList<Integer>();        if(root == null){            return res;        }        res.add(root.val);        res.addAll(preorderTraversal(root.left));                res.addAll(preorderTraversal(root.right));        return res;    }}

Binary Tree Inorder Traversal

public class Solution {    public ArrayList<Integer> inorderTraversal(TreeNode root) {        ArrayList<Integer> res = new ArrayList<Integer>();        if(root == null){            return res;        }        res.addAll(inorderTraversal(root.left));        res.add(root.val);                        res.addAll(inorderTraversal(root.right));        return res;    }}

Binary Tree Postorder Traversal

public class Solution {    public ArrayList<Integer> postorderTraversal(TreeNode root) {        ArrayList<Integer> res = new ArrayList<Integer>();        if(root == null){            return res;        }                res.addAll(postorderTraversal(root.left));               res.addAll(postorderTraversal(root.right));         res.add(root.val);        return res;    }}

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