Help me to transalate this C++ into java

Question

levelorder(root)
  q = empty queue
  q.enqueue(root)
  while not q.empty do
    node := q.dequeue()
    visit(node)
    if node.left ≠ null
      q.enqueue(node.left)
    if node.right ≠ null
      q.enqueue(node.right)and how would I put all the values here instead of in queue it's in an arraylist?

Answer 1

OK, an example:
We have the following tree:       e
    c     f
  b   d     g
aAnd we have your (borrowed) pseudo code:levelorder(root)
  q = empty queue
  q.enqueue(root)
  while not q.empty do
    node := q.dequeue()
    visit(node)
    if node.left ≠ null
      q.enqueue(node.left)
    if node.right ≠ null
      q.enqueue(node.right)Now, when you call levelorder(root), where root = node e, this is what happens:levelorder('e') {               // contents of queue
  new queue                             // [ ]
  queue.enqueue('e')                    // ['e']
  while(queue is not empty) {
    node = queue.dequeue() = 'e'        // [ ]
    if('e'.left is not null) {
      queue.enqueue('c')                // ['c']
    if('e'.right is not null) {
      queue.enqueue('f')                // ['c', 'f']
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'c'        // ['f']
    if('c'.left is not null) {
      queue.enqueue('b')                // ['f', 'b']
    if('c'.right is not null) {
      queue.enqueue('d')                // ['f', 'b', 'd']
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'f'        // ['b', 'd']
    if('f'.left is not null) {
    if('f'.right is not null) {
      queue.enqueue('g')                // ['b', 'd', 'g']
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'b'        // ['d', 'g']
    if('b'.left is not null) {
      queue.enqueue('a')                // ['d', 'g', 'a']
    if('b'.right is not null) {
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'd'        // ['g', 'a']
    if('d'.left is not null) {
    if('d'.right is not null) {
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'g'        // ['a']
    if('g'.left is not null) {
    if('g'.right is not null) {
    // The end of the while here, but since
    // the queue is not empty, we continue
    node = queue.dequeue() = 'a'        // [ ]
    if('a'.left is not null) {
    if('a'.right is not null) {
    // The queue is empty, stop looping
}Now if you look at the order of the dequeue sequence, you'll see the level-order traversal of the tree. Now when you dequeue each node from your queue, you could put those nodes inside an ArrayList (which seems what you're after).
Good luck.