Minimum Depth of Binary Tree

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int minDepth(TreeNode root) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        LinkedList<TreeNode> visiting = new LinkedList<TreeNode>();
        LinkedList<TreeNode> next = new LinkedList<TreeNode>();
        int count = 1;
        if(root == null)
            return 0;
        visiting.add(root);
        while(!visiting.isEmpty()){
            while(!visiting.isEmpty()){
                TreeNode tmp = visiting.poll();
                if(tmp.left == null && tmp.right == null)
                    return count;
                if(tmp.left!=null)
                    next.add(tmp.left);
                if(tmp.right!=null)
                    next.add(tmp.right);
            }
            visiting.addAll(next);
            next.clear();
            count++;
        }
        return 0;
    }
}