minDepth bfs

/**
 * 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 minDepth(TreeNode root) {

            Queue<TreeNode> queue = new LinkedList<>();
            queue.add(root);
            int level = 0;
            if(root == null){
                    return 0;
            }

            while (!queue.isEmpty()) {
                int size = queue.size();
                while (size > 0) {
                    TreeNode presentNode = queue.remove();

                    if (presentNode.left != null) {
                        queue.add(presentNode.left);
                    }
                    if (presentNode.right != null) {
                        queue.add(presentNode.right);
                    }
                    if (presentNode.left == null && presentNode.right == null) {
                        level++;
                        return level;
                    }

                    size--;
                }
                level++;

            }
            return level;
        }
    }