/**
 * 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 int findBottomLeftValue(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        int res = root.val;
        while (!queue.isEmpty()) {
            int size = queue.size();
            res = queue.peek().val;
            while (size > 0) {
                TreeNode t = queue.poll();

                if (t.left != null) {
                    queue.offer(t.left);
                }

                if (t.right != null) {
                    queue.offer(t.right);
                }

                size--;
            }
        }
        return res;
    }
}