zoukankan      html  css  js  c++  java
  • [GeeksForGeeks] Populate inorder successor for all nodes in a binary search tree

    Given a binary search tree with the following tree node definition.

    next points to a node's inorder successor.

    Populate inorder successor for all nodes in this bst.

     1 class TreeNodeWithNext {
     2     int val;
     3     TreeNodeWithNext left, right, next;
     4     public TreeNodeWithNext(int v) {
     5         this.val = v;
     6         this.left = null;
     7         this.right = null;
     8         this.next = null;
     9     }
    10 }

    Recursive solution using reverse in order traversal.

    Since we need to set each node's next to its inorder successor, in order traversal is the natural way to acheive this.

    We can either traverse in order from smaller value nodes to bigger value nodes or vice versa.

     1 private TreeNodeWithNext prev = null;
     2 public void populateInorderSuccessorRecursion(TreeNodeWithNext root) {
     3     if(root == null) {
     4         return;
     5     }
     6     populateInorderSuccessorRecursion(root.left);
     7     if(prev != null) {
     8         prev.next = root;
     9     }
    10     prev = root;
    11     populateInorderSuccessorRecursion(root.right);
    12 }
     1 public class PopulateInorderSuccessor {
     2     private TreeNodeWithNext next = null;
     3     public void populateInorderSuccessorRecursion(TreeNodeWithNext root) {
     4         if(root == null) {
     5             return;
     6         }
     7         populateInorderSuccessorRecursion(root.right);
     8         root.next = next;
     9         next = root;
    10         populateInorderSuccessorRecursion(root.left);
    11     }
    12 }

    Iterative solution.

    Instead of using recursion, we can use a stack to simulate the recursive process and get the following iterative solution.

     1 public void populateInorderSuccessorIterative(TreeNodeWithNext root) {
     2     if(root == null) {
     3         return;
     4     }
     5     TreeNodeWithNext prev = null, curr = root;
     6     Stack<TreeNodeWithNext> stack = new Stack<TreeNodeWithNext>();
     7     while(curr != null || !stack.isEmpty()) {
     8         while(curr != null) {
     9             stack.push(curr);
    10             curr = curr.left;
    11         }
    12         curr = stack.pop();
    13         if(prev != null) {
    14             prev.next = curr;
    15         }
    16         prev = curr;
    17         curr = curr.right;
    18     }
    19 }
  • 相关阅读:
    time模块
    大胆想象! 安全设备专有机房建设思路
    自定义了一个email模块,符合大多数人的使用习惯
    meterpreter持久后门
    使用meterpreter让没有安装python解释器的肉鸡设备执行任意python程序
    入侵感知系列之管理后台发现思路
    入侵感知系列之弱口令检测思路
    入侵感知系列之webshell检测思路
    入侵感知系列之反连检测思路
    智能制造=人工智能?别把智能制造神秘化!
  • 原文地址:https://www.cnblogs.com/lz87/p/7416246.html
Copyright © 2011-2022 走看看