平衡二叉树（B-Tree) C#

2019年3月16日 471次阅读来源: 平衡二叉树

using System;
namespace BTree
{
class Node//二叉树结点数据类型
{
public int data;//数据
public Node lchild;//左子树
public Node rchild;//右子树
public Node(int i, Node l, Node r)
{
data = i;
lchild = l;
rchild = r;
}
}
class BTree
{
public Node ROOT;
public BTree()
{
ROOT = null;
}
public void insert(int element)
{
Node tmp, parent = null, currentNode = null;
find(element, ref parent, ref currentNode);
if (currentNode != null)//如果currentNode不为空值说明currentNode.info==element，是重复元素
{
Console.WriteLine(“Duplicates words not allowed”);
return;
}
else//如果currentNode为空值时插入新结点
{
tmp = new Node(element, null, null);//tmp为新节点，lchild和rchild指正均为空
if (parent == null)//如果parent结点为空，说明树为空，则tmp作为根结点
ROOT = tmp;
else
if (element < parent.data)//如果parent不为空，则比较parent.data和element的大小
parent.lchild = tmp;
else
parent.rchild = tmp;
}
}
public void find(int element, ref Node parent, ref Node currentNode)//寻找元素
{
currentNode = ROOT;
parent = null;
while ((currentNode != null) && (currentNode.data != element))
{//当currentNode指针所指的当前结点不为空时，或者当前结点的info不为element时循环
parent = currentNode;//将parent指针指向currentNode指向的当前结点
if (element < currentNode.data)
currentNode = currentNode.lchild;//element比current.data小时，将currentNode指向左子树
else
currentNode = currentNode.rchild;
}
}
public void delete(int element)
{
Node parent = null, currentNode = null;
find(element, ref parent, ref currentNode);
if (currentNode != null)//找到目标结点
{
if (currentNode.lchild == null && currentNode.rchild == null)//如果目标结点的左子树和右子树均为空
{
if (parent == null)//如果目标结点为根结点
ROOT = null;
//Release currentNode
else
{
if (parent.lchild == currentNode)
parent.lchild = null;
else
parent.rchild = null;
//Release currentNode
}
}
else if ((currentNode.lchild == null && currentNode.rchild != null)
|| (currentNode.lchild != null && currentNode.rchild == null))//如果目标结点有一棵子树
{
if (parent == null)
{
if (currentNode.lchild != null)
ROOT = currentNode.lchild;
else
ROOT = currentNode.rchild;
//Release currentNode
}
else
{
if (parent.lchild == currentNode)
if (currentNode.lchild != null)
parent.lchild = currentNode.lchild;
else
parent.lchild = currentNode.rchild;
else
if (currentNode.lchild != null)
parent.rchild = currentNode.lchild;
else
parent.rchild = currentNode.rchild;
//Release currentNode
}
}
else if (currentNode.lchild != null && currentNode.rchild != null)//如果目标结点有两颗子树
{
Node inorder_suc = currentNode.rchild;
parent = currentNode;
while (inorder_suc.lchild != null)//寻找currentNode右子树的最左子树
{
parent = inorder_suc;
inorder_suc = inorder_suc.lchild;
}
currentNode.data = inorder_suc.data;
if (inorder_suc.lchild == null && inorder_suc.rchild == null)//如果inorder_suc的左子树和右子树均为空
{
if (parent.lchild == inorder_suc)
parent.lchild = null;
else
parent.rchild = null;
//Release currentNode
}
if (inorder_suc.lchild == null || inorder_suc.rchild == null)//如果inorder_suc有一棵子树
{
if (parent.lchild == inorder_suc)
if (inorder_suc.lchild != null)
parent.lchild = inorder_suc.lchild;
else
parent.lchild = inorder_suc.rchild;
else
if (inorder_suc.lchild != null)
parent.rchild = inorder_suc.lchild;
else
parent.rchild = inorder_suc.rchild;
//Release currentNode
}
}
}
}
public void balanceTree(ref Node pivot, ref int BF)
{
Node X, Y, parent = null, currentNode = null;
if (BF < 0)//if tree is initially right heavy
{
X = pivot.rchild;
if (getHeight(X.lchild, ref pivot, ref BF) < getHeight(X.rchild, ref pivot, ref BF))
{//the new node is inserted in the right subtree of X
find(pivot.data, ref parent, ref currentNode);
if (pivot != ROOT)
{
if (parent.lchild == pivot)
parent.lchild = X;
else
parent.rchild = X;
}
else
ROOT = X;
pivot.rchild = X.lchild;
X.lchild = pivot;
}
else//the new node is inserted in the left subtree of x
{
Y = X.lchild;
X.lchild = Y.rchild;
Y.rchild = X;
pivot.rchild = Y;
//repeat once the code above when getHeight(X.lchild) < getHeight(X.rchild)
X = pivot.rchild;
find(pivot.data, ref parent, ref currentNode);
if (pivot != ROOT)
{
if (parent.lchild == pivot)
parent.lchild = X;
else
parent.rchild = X;
}
else
ROOT = X;
pivot.rchild = X.lchild;
X.lchild = pivot;
}
}
else//if the tree is initially left heavy
{
X = pivot.lchild;
if (getHeight(X.lchild, ref pivot, ref BF) > getHeight(X.rchild, ref pivot, ref BF))
{//the new node is inserted in the left subtree of X
find(pivot.data, ref parent, ref currentNode);
if (pivot != ROOT)
{
if (parent.lchild == pivot)
parent.lchild = X;
else
parent.rchild = X;
}
else
ROOT = X;
pivot.lchild = X.rchild;
X.rchild = pivot;
}
else//the new node is inserted in the right subtree of x
{
Y = X.rchild;
X.rchild = Y.lchild;
Y.lchild = X;
pivot.lchild = Y;
//repeat once the code above when getHeight(X.lchild) > getHeight(X.rchild)
X = pivot.lchild;
find(pivot.data, ref parent, ref currentNode);
if (pivot != ROOT)
{
if (parent.lchild == pivot)
parent.lchild = X;
else
parent.rchild = X;
}
else
ROOT = X;
pivot.lchild = X.rchild;
X.rchild = pivot;
}
}
}
public int getHeight(Node ptr, ref Node pivot, ref int BF)
{
int lHeight = 0, rHeight = 0;
if (ROOT == null && pivot != null)
return 0;
else
{
if (ptr!= null)
{
lHeight = getHeight(ptr.lchild, ref pivot, ref BF);
rHeight = getHeight(ptr.rchild, ref pivot, ref BF);
if (Math.Abs(lHeight – rHeight) > 1 && pivot == null)//notice here!! “pivot==null”,otherwise make a mistake
{//here get pivot and balance factor
pivot = ptr;
BF = lHeight – rHeight;
}
return (lHeight > rHeight ? lHeight + 1 : rHeight + 1);
}
else
return 0;
}
}
public void printTree(Node ptr, int level)//输出二叉树
{
if (ptr == null)
return;
else
{
if (ptr.rchild != null)
printTree(ptr.rchild, level + 1);
for (int i = 0; i < level; i++)
Console.Write(” “);
Console.WriteLine(ptr.data);
if (ptr.lchild != null)
printTree(ptr.lchild, level + 1);
}
}
}
class Program
{
static void Main(string[] args)
{
char ch;
int data, BF;
Node pivot;
BTree b = new BTree();
while (true)
{
Console.Clear();
BF = 0;
pivot = null;
b.getHeight(b.ROOT, ref pivot, ref BF);
if (pivot != null)
b.balanceTree(ref pivot, ref BF);
Console.WriteLine(“print B-Tree:”);
b.printTree(b.ROOT, 1);
Console.WriteLine(“——MENU——“);
Console.WriteLine(“1. inseret data”);
Console.WriteLine(“2. delete data”);
Console.WriteLine(“3. Exit”);
ch = char.Parse(Console.ReadLine());
switch (ch)
{
case ‘1’:
{
Console.Write(“enter a data:”);
data = int.Parse(Console.ReadLine());
b.insert(data);
break;
}
case ‘2’:
{
Console.WriteLine(“enter a data:”);
data = int.Parse(Console.ReadLine());
b.delete(data);
break;
}
case ‘3’:
return;
default:
{
Console.WriteLine(“Invalid option”);
break;
}
}
}
}
}
}

    原文作者：平衡二叉树
    原文地址: https://blog.csdn.net/zen_chou/article/details/3016471
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