zoukankan      html  css  js  c++  java
  • Leetcode 116. Populating Next Right Pointers in Each Node

    https://leetcode.com/problems/populating-next-right-pointers-in-each-node/

    Medium

    You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:

    struct Node {
      int val;
      Node *left;
      Node *right;
      Node *next;
    }
    

    Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

    Initially, all next pointers are set to NULL.

    Example:

    Input: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}
    
    Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1}
    
    Explanation: Given the above perfect binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.
    

    Note:

    • You may only use constant extra space.
    • Recursive approach is fine, implicit stack space does not count as extra space for this problem.

     1 """
     2 # Definition for a Node.
     3 class Node:
     4     def __init__(self, val, left, right, next):
     5         self.val = val
     6         self.left = left
     7         self.right = right
     8         self.next = next
     9 """
    10 class Solution:
    11     def connect(self, root: 'Node') -> 'Node':
    12         if root is None:
    13             return None
    14         
    15         head = root
    16         list_current = [root]
    17         
    18         while list_current:
    19             next_level = []
    20             
    21             for i in range( len( list_current ) ):
    22                 if i + 1 < len(list_current):
    23                     list_current[i].next = list_current[i + 1]
    24                 
    25                 if list_current[i].left:
    26                     next_level.append(list_current[i].left)
    27                 if list_current[i].right:
    28                     next_level.append(list_current[i].right)
    29             
    30             list_current = next_level
    31         
    32         return head            
    View Python Code
  • 相关阅读:
    Swift和OC混编
    Swift逃逸闭包之见解
    百度地图集成
    hitTest和pointInside和CGRectContainsPoint
    Bitcode问题
    ReactiveCocoa常用方法
    iOS之图文混排
    tableview cell添加3D动画
    ReactiveCocoa总结
    Math类常用方法(Java)
  • 原文地址:https://www.cnblogs.com/pegasus923/p/11227367.html
Copyright © 2011-2022 走看看