Binary Tree Zigzag Level Order Traversal (bazinga)

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
            	boolean inorder=true;
        List<List<Integer>> list=new ArrayList<List<Integer>>();
        if(root==null) return list;
        List<Integer> level=new ArrayList<Integer>();
        level.add(root.val);
        list.add(level);
        level=new ArrayList<Integer>();
        Queue<TreeNode> queue=new LinkedList<TreeNode>();
        if(root.left!=null) queue.add(root.left);
        if(root.right!=null) queue.add(root.right);
        queue.add(null);
        inorder=false;
        while(true){
        	if (queue.peek()==null) {
        		queue.poll();
        		if (queue.isEmpty()) {
					break;
				}
        		if(inorder) {list.add(level);inorder=false;}
        		else {
        			list.add(reverse(level));inorder=true;
				}
        		level=new ArrayList<Integer>();
        		queue.add(null);
			}else{
				TreeNode tmp=queue.poll();
				level.add(tmp.val);
		        if(tmp.left!=null) queue.add(tmp.left);
		        if(tmp.right!=null) queue.add(tmp.right);
			}
        }
        if(!level.isEmpty()){
        	if(inorder) {list.add(level);inorder=false;}
    		else {
    			list.add(reverse(level));inorder=true;
			}
        }
        return list;
    }
    private List<Integer> reverse(List<Integer> list){
    	List<Integer> ret=new ArrayList<Integer>();
    	for (int i = list.size()-1; i >= 0; i--) {
			ret.add(list.get(i));
		}
    	return ret;
    }
}