LeetCode Medium: Binary Tree Level Order Traversal

Here is my solution to LeetCode Problem #102: Binary Tree Level Order Traversal based on BFS traversal with modification -

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> res = new ArrayList<>();
        if (root == null)
            return res;
        Queue<TreeNode> q = new LinkedList<>();
        q.add(root);
        while(!q.isEmpty()) {
            int levelSize = q.size();
            List<Integer> level = new ArrayList<> ();
            for (int i=0; i<levelSize; i++) {
                TreeNode current = q.remove();
                level.add(current.val);
                if (current.left != null) q.add(current.left);
                if (current.right != null) q.add(current.right);
            }
            res.add(level);
        }
        
        return res;
    }
}

Try these related problems too:

https://chandniverma.blogspot.com/2020/06/leetcode-medium-binary-tree-right-side.html