​LeetCode刷题实战103：二叉树的锯齿形层次遍历

class Solution {
    public List<List> zigzagLevelOrder(TreeNode root) {
        
        List<List> L=new ArrayList<List>();
        if(root==null){
            return L;
        }
        Queue q=new LinkedList();
        q.offer(root);
        int count=1;
        
        while(!q.isEmpty()){
            
            List list=new ArrayList();
            int size=q.size();
            for(int i=0;i                TreeNode temp=q.poll();
                if(temp.left!=null){
                    q.offer(temp.left);
                }
                
                if(temp.right!=null){
                    q.offer(temp.right);
                }
               
                
                list.add(temp.val);
            }
            if(count%2!=0){
                 L.add(list);
            }else{
                Collections.reverse(list);
                L.add(list);
            }
            count++;
           
        }
        return L;
    }
}