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:
    MySQL多表查询回顾
    本地SQL查询
    QBC查询
    HQL查询
    Hibernate多对多操作
    Hibernate一对多操作
    表与表之间关系回顾
    x$bh视图
    dba 和 rdba 转载
    What you can talk
  • 原文地址:https://www.cnblogs.com/anxin6699/p/7289862.html
Copyright © 2011-2022 走看看