剑指 Offer 55 - I. 二叉树的深度

package leetcode;

public class offer_55_1 {
    int count=0;
    int maxlength=0;
    public int maxDepth(TreeNode root) {
        backtrace(root);
        return maxlength;
    }
    
    public void backtrace(TreeNode root) {
        //当前节点为空，判断最大长度
        if(root==null) {
            if(count>maxlength) {
                maxlength=count;
            }
        }else {
            count=count+1;
            backtrace(root.left);
            backtrace(root.right);
            //左右节点都为空说明已是叶子节点，则层数减一
            count=count-1;
        }
    }
}