zoukankan      html  css  js  c++  java
  • LeetCode 776. Split BST

    原题链接在这里:https://leetcode.com/problems/split-bst/

    题目:

    Given a Binary Search Tree (BST) with root node root, and a target value V, split the tree into two subtrees where one subtree has nodes that are all smaller or equal to the target value, while the other subtree has all nodes that are greater than the target value.  It's not necessarily the case that the tree contains a node with value V.

    Additionally, most of the structure of the original tree should remain.  Formally, for any child C with parent P in the original tree, if they are both in the same subtree after the split, then node C should still have the parent P.

    You should output the root TreeNode of both subtrees after splitting, in any order.

    Example 1:

    Input: root = [4,2,6,1,3,5,7], V = 2
    Output: [[2,1],[4,3,6,null,null,5,7]]
    Explanation:
    Note that root, output[0], and output[1] are TreeNode objects, not arrays.
    
    The given tree [4,2,6,1,3,5,7] is represented by the following diagram:
    
              4
            /   
          2      6
         /     / 
        1   3  5   7
    
    while the diagrams for the outputs are:
    
              4
            /   
          3      6      and    2
                /            /
               5   7         1
    

    Note:

    1. The size of the BST will not exceed 50.
    2. The BST is always valid and each node's value is different.

    题解:

    If current node value is larger than V, then perfor DFS on its left subtree.

    The returned value is an array of 2 trees. First one is smaller than or equal to V, second is larger than V.

    Then current node left child should be first one. Now current node including its left subtree are all smaller than or equal to V, use it as new first element of array, and existing second element to return.

    Vice versa.

    Time Complexity: O(h).

    Space: O(h).

    AC Java:

     1 /**
     2  * Definition for a binary tree node.
     3  * public class TreeNode {
     4  *     int val;
     5  *     TreeNode left;
     6  *     TreeNode right;
     7  *     TreeNode(int x) { val = x; }
     8  * }
     9  */
    10 class Solution {
    11     public TreeNode[] splitBST(TreeNode root, int V) {
    12         if(root == null){
    13             return new TreeNode[]{null, null};
    14         }
    15 
    16         if(root.val > V){
    17             TreeNode [] left = splitBST(root.left, V);
    18             root.left = left[1];
    19             return new TreeNode[]{left[0], root};
    20         }else{
    21             TreeNode [] right = splitBST(root.right, V);
    22             root.right = right[0];
    23             return new TreeNode[]{root, right[1]};
    24         }
    25     }
    26 }

    类似Delete Node in a BST.

  • 相关阅读:
    go视频提取音频
    ffmpeg常用命令 转
    mac安装homebrew
    go读取键盘输入两种方式
    静态方法加锁,和非静态方法加锁区别
    Java类锁和对象锁实践和内部私有锁关联
    Java基础】并发
    一步一步掌握线程机制(六)---Atomic变量和Thread局部变量
    compareAndSet() 注意点
    Java JUC之Atomic系列12大类实例讲解和原理分解
  • 原文地址:https://www.cnblogs.com/Dylan-Java-NYC/p/11145009.html
Copyright © 2011-2022 走看看