Java實現求二叉樹的高度

package com.qiye;


import java.util.LinkedList;
import java.util.Queue;
class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
  }


public class Solution2 {
    /**
     * 遞歸求解
     * 返回樹的高度
     * @param root TreeNode類 樹根節點
     * @return int整型
     */
    public int getTreeHeight1 (TreeNode root) {
        if(root == null){
            return 0;
        }
        int left = getTreeHeight1(root.left);
        int right = getTreeHeight1(root.right);
        return left > right? left + 1 : right + 1;
    }

    /***
     * 非遞歸求解
     * @param root
     * @return
     */
    public int getTerrHeight(TreeNode root){
        if(root == null){
            return 0;
        }
        //使用count進行層級統計。
        //nextCount保存的是每層遍歷後新增到隊列中的元素數量。
        //如果count++ = nextCount 就說明將該層遍歷完了 deep++ nextCount等於隊列中保存的下一層的所有結點數目。
        //以此類推
        int deep = 0,count = 0,nextCount = 1;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()){
            TreeNode treeNode = queue.poll();
            count ++;
            if(treeNode.left != null){
                queue.add(treeNode.left);
            }
            if(treeNode.right != null){
                queue.add(treeNode.right);
            }
            if(count == nextCount){
                nextCount = queue.size();
                count = 0;
                deep ++;
            }
        }
        return deep;
    }
    public static void main(String[] args) {

        TreeNode root = new TreeNode();
        TreeNode left = new TreeNode();
        TreeNode right = new TreeNode();
        TreeNode left_left = new TreeNode();
        TreeNode left_right = new TreeNode();
        TreeNode right_left = new TreeNode();
        TreeNode right_right = new TreeNode();

        root.right = right;
        root.left = left;
        root.left.left = left_left;
        root.left.right = left_right;
        root.right.left = right_left;
        root.right.right = right_right;
        System.out.println(new Solution2().getTreeHeight1(root));
        System.out.println(new Solution2().getTerrHeight(root));
    }
}