题解 | #按之字形顺序打印二叉树#

/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
      Queue<TreeNode> q = new LinkedList<>();
     ArrayList<ArrayList<Integer>> list1 = new ArrayList<>();
      if(pRoot == null){
          return list1;
      }
        TreeNode node = pRoot;
        q.offer(node);
        int s = 0;
        while(!q.isEmpty()){
            int size = q.size();
            ArrayList<Integer> list = new ArrayList<>();
            for(int i = 0;i < size;i++){
                TreeNode cur = q.poll();
                if((s%2) == 0){
                    list.add(cur.val);
                }else{
                    list.add(0,cur.val);
                }
                if(cur.left != null){
                    q.offer(cur.left);
                }
                if(cur.right != null){
                    q.offer(cur.right);
                }
           }
            s++;
            list1.add(list);
        }
        return list1;
    }

}