Binary search tree traversal that compares two pointers for equality

Question

I\'m reading the Cormen algorithms book (binary search tree chapter) and it says that there are two ways to traverse the tree without recursion:

using sta

Answer 1

Sure thing. You didn't say what kind of traversal you wanted, but here's the pseudocode for an in-order traversal.

t = tree.Root;
while (true) {
  while (t.Left != t.Right) {
    while (t.Left != null) {   // Block one.
      t = t.Left;
      Visit(t);
    }
    if (t.Right != null) {     // Block two.
      t = t.Right;
      Visit(t);
    }
  }

  while (t != tree.Root && (t.Parent.Right == t || t.Parent.Right == null)) {
    t = t.Parent;
  }
  if (t != tree.Root) {        // Block three.
    t = t.Parent.Right;
    Visit(t);
  } else {
    break;
  }
}

To get pre- or post-order, you rearrange the order of the blocks.