剑指Offer 55 二叉树的深度

二叉树的深度

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。

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def __init__(self):
        self.maxlen = 0
    
    def preOrder(self,root,length):
        if root != None:
            length += 1
            self.preOrder(root.left,length)
            self.preOrder(root.right,length)
            if root.left == None and root.right == None:
                self.maxlen = max(self.maxlen,length)
            length -= 1
        
    def TreeDepth(self, pRoot):
        if pRoot == None:
            return 0
        self.preOrder(pRoot,0)
        return self.maxlen
        # write code here

 

Java版代码，leetcode地址：

class Solution {
    int maxLen = 0;

    public void preOrder(TreeNode root, int length) {
        if (root != null) {
            length++;// 遍历下一层节点，层数+1
            preOrder(root.left, length);
            preOrder(root.right, length);
            if (root.left == null && root.right == null) {
                // 叶子节点，计算一次最大深度
                maxLen = Integer.max(maxLen, length);
            }
            length--;// 遍历完叶子节点，回退，层数-1
        }
    }

    public int maxDepth(TreeNode root) {
        if (root == null) {
            return 0;
        }
        preOrder(root, 0);
        return maxLen;
    }
}

 

 

平衡二叉树

输入一棵二叉树，判断该二叉树是否是平衡二叉树。

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    def __init__(self):
        self.isBalanced = True
        
    def height(self,root):
        if root == None or not self.isBalanced:
            return 0
        left = self.height(root.left)
        right = self.height(root.right)
        if abs(left - right) > 1:
            self.isBalanced = False
        return 1 + max(left,right)
        
    def IsBalanced_Solution(self, pRoot):
        self.height(pRoot)
        return self.isBalanced
        # write code here

 

Java版代码，leetcode地址：

class Solution {
    boolean isBalanced = true;

    public int height(TreeNode root) {
        if (root == null || !isBalanced) {
            return 0;
        }
        int left = height(root.left);
        int right = height(root.right);
        if (Math.abs(left - right) > 1) {
            isBalanced = false;
        }
        return 1 + Integer.max(left, right);
    }

    public boolean isBalanced(TreeNode root) {
        height(root);
        return isBalanced;
    }
}