LevelOrderBinaryTree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> answer = new LinkedList<>();
        if(root==null)
            return answer;
        Queue<TreeNode> cache = new LinkedList<>();
        cache.add(root);
        while(!cache.isEmpty())
        {
            List<Integer> currLevel = new LinkedList<>();
            int n = cache.size();
            for(int i =0;i<n;i++)
            {
                TreeNode temp=cache.poll();
                
                currLevel.add(temp.val);
                if(temp.left!=null)
                    cache.add(temp.left);
                if(temp.right!=null)
                    cache.add(temp.right);
            }
            answer.add(currLevel);
        }
        return answer;
    }
}