145. Binary Tree Postorder Traversal|Time:O(n)|Space:O(n)

// Problem: https://leetcode.com/problems/binary-tree-postorder-traversal/
// Solution adapted from: https://www.youtube.com/watch?v=qT65HltK2uE

public class PostorderRecursive {

    public static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int x) { val = x; }
    }

    public static void postOrder(TreeNode root){
        if(root == null){
            return;
        }

        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static void main(String args[]){

        TreeNode root = new TreeNode(10);
        root.left = new TreeNode(8);
        root.right = new TreeNode(2);
        root.left.left = new TreeNode(3);
        root.left.right = new TreeNode(5);
        root.right.left = new TreeNode(7);

        postOrder(root);
        // Expected output: 3 5 8 7 2 10
    }
}