static void Main(string[] args)
{
//PowerTreeNode root = new PowerTreeNode(1);
//root.left = new PowerTreeNode(2);
//root.right = new PowerTreeNode(3);
//root.left.left = new PowerTreeNode(4);
//root.right.left = new PowerTreeNode(5);
//root.right.right = new PowerTreeNode(6);
//root.left.left.left = new PowerTreeNode(7);
LinkTreeNode linkRoot = new LinkTreeNode(1);
linkRoot.left = new LinkTreeNode(2);
linkRoot.right = new LinkTreeNode(3);
linkRoot.left.left = new LinkTreeNode(4);
linkRoot.right.left = new LinkTreeNode(5);
linkRoot.right.right = new LinkTreeNode(6);
linkRoot.left.left.left = new LinkTreeNode(7);
linkRoot.right.right.left = new LinkTreeNode(8);
Console.WriteLine(String.Join(" ", ZigZagTraversal.TraverseSimple(linkRoot)));
//TreeNode simpleRoot = new TreeNode(1);
//simpleRoot.left = new TreeNode(2);
//simpleRoot.right = new TreeNode(3);
//simpleRoot.left.left = new TreeNode(4);
//simpleRoot.right.left = new TreeNode(5);
//simpleRoot.right.right = new TreeNode(6);
//simpleRoot.left.left.left = new TreeNode(7);
//Console.WriteLine(String.Join(" ", ZigZagTraversal.TraverseWithSimpleNode(simpleRoot)));
//int[] cards = new int[54];
//for (int i = 0; i < 54; i++) {
// cards[i] = i;
//}
//ShuffleCard.Go(cards);
//Console.WriteLine(String.Join(" ", cards));
Console.ReadLine();
}
// #2 in 1/29 discussion
// O(1) space
// change structure of node with link only in one direction
public static List<int> TraverseSimple(LinkTreeNode root) {
if (root == null) return new List<int>();
List<int> res = new List<int>();
LinkTreeNode curr = root;
LinkTreeNode head = null; // head node in next level
bool rightToLeft = true; // direction, view first level as from right to left
// two children of current node waiting for linking
LinkTreeNode p = null;
LinkTreeNode q = null;
while (curr != null) {
res.Add(curr.val);
p = rightToLeft ? curr.right : curr.left;
q = rightToLeft ? curr.left : curr.right;
// link children
if (p != null) {
if(head != null) {
p.next = head;
}
head = p;
}
if (q != null){
if (head != null) {
q.next = head;
}
head = q;
}
// move to next level
if (curr.next == null) {
curr.next = head;
head = null;
rightToLeft = !rightToLeft;
}
curr = curr.next;
}
return res;
}