Level-order traversal of a binary tree

问题

I want to perform level-order traversal of a binary tree. Hence, for a given tree, say:

the output would be:

3 2 1 4 6 10

I understand that I could use some sort of queue, but what is the algorithm to do this in C recursively? Any help appreciated.

回答1:

The graph algorithm is called Breadth First Search, it uses a queue to perform the level-order traversal, here is the pseudo-code

void breadth_first(Node root)
{
  Queue q;
  q.push(root);
  breadth_first_recursive(q)
}

void breadth_first_recursive(Queue q)
{
  if q.empty() return;
  Node node = q.pop()
  print Node
  if (n.left) q.push(n.left)
  if (n.right) q.push(n.right)
  breadth_first_recursive(q)
}

回答2:

here to you the pseudocode from wikipedia

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)

you can then transform it into C that is trivial...

回答3:

Here code (no recursive function) from C5 library : C5 UserGuideExamples - TreeTraversal

public static void BreadthFirst(Tree<T> t, Action<T> action)
{
  IQueue<Tree<T>> work = new CircularQueue<Tree<T>>();
  work.Enqueue(t);
  while (!work.IsEmpty)
  {
    Tree<T> cur = work.Dequeue();
    if (cur != null)
    {
      work.Enqueue(cur.t1);
      work.Enqueue(cur.t2);
      action(cur.val);
    }
  }
}

回答4:

Another No-recursive apporoach..

void LevelOrder(node * root)
{
  queue<node *> q;
    node *n=new node;
    n=root;
    while(n)
    {
        cout<<n->data<<" ";
        if(n->left)
            q.push(n->left);
        if(n->right)
            q.push(n->right);
        n=q.front();
        q.pop();


    }



}

回答5:

void    levelorder    (Node *root)
{
   if(!root)
       return;
   queue<Node*>    Q;
   Q.push(root);
   while(!Q.empty())
   {
    Node *current   =    Q.front();//returns the front element in queue
    cout <<current->data;//printing the front node of queue
    if(current->left!=NULL)
      Q.push(current->left);//pushing left child
    if(current->right!=NULL)
      Q.push(current->right);//pushing right child
     Q.pop();//removing front element from queue.
   }
}

来源：https://stackoverflow.com/questions/15166617/level-order-traversal-of-a-binary-tree

标签

algorithm

binary-tree