Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

 

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxDepth(TreeNode root) {
    	if (root == null) {
    		return 0;
    	}
    	int res = 0;
        int cur = 1;
        int next = 0;
        LinkedList<TreeNode> linkedList = new LinkedList<TreeNode>();
        linkedList.add(root);
        while (!linkedList.isEmpty()) {
        	TreeNode poll = linkedList.poll();
        	cur--;
        	if (poll.left != null) {
        		linkedList.add(poll.left);
        		next++;
        	}
        	if (poll.right != null) {
        		linkedList.add(poll.right);
        		next++;
        	}
        	if (cur == 0) {
        		cur = next;
        		next = 0;
        		res++;
        	}
        }
        return res;
    }
}