package problems.medium;
import problems.utils.TreeNode;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
/**
* Created by sherxon on 1/8/17.
*/
public class ZigZagOrderLevelTraversalBST {
public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
List<List<Integer>> list = new ArrayList<>();
if (root == null) return list;
List<Integer> l = new LinkedList<>();
l.add(root.val);
list.add(l);
LinkedList<TreeNode> q = new LinkedList<>();
int level = 1;
q.add(root);
boolean flag = false;
while (!q.isEmpty()) {
TreeNode x = q.removeFirst();
if (x.right != null) q.addLast(x.right);
if (x.left != null) q.addLast(x.left);
level--;
if (level == 1 && !q.isEmpty()) {
LinkedList<Integer> ll = new LinkedList<>();
level += q.size();
for (TreeNode xx : q) {
if (flag)
ll.addFirst(xx.val);
else
ll.addLast(xx.val);
}
flag = !flag;
list.add(ll);
}
}
return list;
}
}