/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
import java.util.ArrayList;
import java.util.Iterator;
public class Solution {
public ArrayList<ArrayList<Integer>> levelOrder(TreeNode root) {
// Start typing your Java solution below
// DO NOT write main() function
ArrayList<ArrayList<Integer>> list= new ArrayList<ArrayList<Integer>>();
if(root == null)
return list;
ArrayList<TreeNode> current = new ArrayList<TreeNode>();
current.add(root);
ArrayList<TreeNode> nextLevel = new ArrayList<TreeNode>();
while(current.size() != 0){
ArrayList<Integer> temp = new ArrayList<Integer>();
nextLevel = new ArrayList<TreeNode>();
for (Iterator<TreeNode> it = current.iterator(); it.hasNext();) // use iterator to store node
{
TreeNode node = it.next();
temp.add(node.val);
if(node.left != null)
{
nextLevel.add(node.left);
}
if(node.right != null)
{
nextLevel.add(node.right);
}
}
list.add(temp);
current = nextLevel;
}
return list;
}
}