二叉树的深度

题目描述

输入一棵二叉树，求该树的深度。从根结点到叶结点依次经过的结点（含根、叶结点）形成树的一条路径，最长路径的长度为树的深度。

简洁代码

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    public int TreeDepth(TreeNode root) {
         if(root == null) return 0;
        int leftDepth = TreeDepth(root.left);
        int rightDepth = TreeDepth(root.right);
        return leftDepth > rightDepth? leftDepth + 1:rightDepth + 1;//这里要加1的原因是深度数的是节点的个数
    }
}

public class BinaryTreeDepth {
     static class  TreeNode{
        int val = 0;
        TreeNode left = null;
        TreeNode right = null;

        public TreeNode(int val) {
            this.val = val;
        }
    }

    public int treeDepth(TreeNode root){
         if(root == null){
             System.out.println("root为空");
         }else {
             System.out.println("root--------------:" + root.val);
         }
        if(root == null) return 0;
        int leftDepth = treeDepth(root.left);
        System.out.println("leftDepth:" + leftDepth);
        int rightDepth = treeDepth(root.right);
        System.out.println("rightDepth:" + rightDepth);
        return leftDepth > rightDepth? leftDepth + 1:rightDepth + 1;

    }

    public static void main(String[] args){
        BinaryTreeDepth binaryTreeDepth = new BinaryTreeDepth();
        TreeNode treeNode = new TreeNode(1);
        treeNode.left = new TreeNode(2);
        treeNode.right = new TreeNode(3);
        treeNode.left.left = new TreeNode(4);
        treeNode.left.right = new TreeNode(5);
        int i = binaryTreeDepth.treeDepth(treeNode);
        System.out.println(i);


    }
}

root--------------:1
root--------------:2
root--------------:4
root为空
==========================左子树遍历完成
leftDepth:0==>root = 4.left
root为空
rightDepth:0=>root = 4.right
leftDepth:1==>root = 2.left = 4
root--------------:5==>2.right = 5
root为空==>root = 5.left
leftDepth:0==>root = 5.left
root为空==>root = 5.right
rightDepth:0==>root = 5.right
rightDepth:1==>root = 2.right = 5
leftDepth:2==>root = 1.left = 2<====================左子树的深度为leftDephth + 1 = 3
root--------------:3==>root = 1.right = 3
root为空==>root = 3.left 
leftDepth:0==>root = 3.left 
root为空==>root = 3.right
rightDepth:0==>root = 3.right
rightDepth:1==>root = 1.right = 3<====================右子树的深度为rightDepth + 1 = 2
3

Process finished with exit code 0