lc513——找树左下角的值

/**
 * 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 a=0;
        while(!queue.isEmpty())
        {   
            int size=queue.size();
            for(int i=0;i<size;i++)
            {
                TreeNode poll=queue.poll();
                if(i==0)
                {
                    a=poll.val;
                }
                if(poll.left!=null)
                {
                    queue.add(poll.left);
                }
                if(poll.right!=null)
                {
                    queue.add(poll.right);
                }

            }
        }
    return a;
    }