zoukankan      html  css  js  c++  java
  • [Leetcode] Binary tree-- 563. Binary Tree Tilt

    Given a binary tree, return the tilt of the whole tree.

    The tilt of a tree node is defined as the absolute difference between the sum of all left subtree node values and the sum of all right subtree node values. Null node has tilt 0.

    The tilt of the whole tree is defined as the sum of all nodes' tilt.

    Example:

    Input: 
             1
           /   
          2     3
    Output: 1
    Explanation: 
    Tilt of node 2 : 0
    Tilt of node 3 : 0
    Tilt of node 1 : |2-3| = 1
    Tilt of binary tree : 0 + 0 + 1 = 1


    Solution:
    1. naive solution,  recursively get every node's tilt  by treating every node as a root and traverse the left subtree and right subtree,
    there is gonna be too much repetitions
    1   #1st niave recursive
    2         def findTiltSumHelper(root):
    3             if root is None:
    4                 return 0
    5             return findTiltSumHelper(root.left) + root.val + findTiltSumHelper(root.right)
    6         
    7         if root is None:
    8             return 0
    9         return self.findTilt(root.left) + abs(findTiltSumHelper(root.left) - findTiltSumHelper(root.right)) + self.findTilt(root.right)

    2. 

     1         def findTiltSumHelper(root):
     2             if root is None:
     3                 return 0
     4             left = findTiltSumHelper(root.left) 
     5             right = findTiltSumHelper(root.right)
     6             tmp = abs(left - right)
     7             self.ansSum += tmp
     8             return left + root.val + right
     9         
    10         findTiltSumHelper(root)
    11         return  self.ansSum


  • 相关阅读:
    python 字符串中的%s与format
    python中的virtualenv是干嘛的?
    grep 与 find 简单命令
    git merge 和 git rebase的区别
    git stash的用法
    git push的用法
    git pull与git fetch的区别
    辟谣平台 踩坑记(一)
    微信JS-SDK开发 入门指南
    linux 写U盘出现的问题
  • 原文地址:https://www.cnblogs.com/anxin6699/p/7289862.html
Copyright © 2011-2022 走看看