前序遍历二叉树,中序遍历二叉树,后序遍历二叉树 c#实现
using System.Collections.Generic;
using System.Collections;
class BiTree
{
public BiTree leftChild;
public BiTree rightChild;
public object Data;
public BiTree(object aData)
{
Data = aData;
}
}
class TestUtil
{
public static void Main()
{
BiTree root = new BiTree("1");
BiTree n1 = new BiTree("2");
BiTree n2 = new BiTree("3");
BiTree n3 = new BiTree("4");
BiTree n4 = new BiTree("5");
BiTree n5 = new BiTree("6");
BiTree n6 = new BiTree("7");
root.leftChild = n1;
root.rightChild = n2;
n1.leftChild = n3;
n1.rightChild = n4;
n2.leftChild = n5;
n2.rightChild = n6;
//PreTravelCur(root);
Console.WriteLine("中序:");
MidTravelStack(root);
Console.WriteLine("前序:");
PreTravelStack(root);
Console.WriteLine("后序:");
LastTravelStack(root);
Console.Read();
}
/// <summary>
/// 前序遍历,递归
/// </summary>
/// <param name="tree"></param>
public static void PreTravelCur(BiTree tree)
{
if (tree != null)
{
Console.WriteLine(tree.Data);
PreTravelCur(tree.leftChild);
PreTravelCur(tree.rightChild);
}
}
/// <summary>
/// 中序遍历
/// </summary>
/// <param name="tree"></param>
public static void MidTravelStack(BiTree tree)
{
if (tree == null)
{
return;
}
Stack<object> stack = new Stack<object>();
BiTree p = tree;
do
{
while (p != null)
{
stack.Push(p);
p = p.leftChild;
}
p =(BiTree) stack.Pop();
Console.WriteLine(p.Data);
p = p.rightChild;
} while (stack.Count > 0|| p != null);
}
/// <summary>
/// 前序遍历
/// </summary>
/// <param name="tree"></param>
public static void PreTravelStack(BiTree tree)
{
if (tree == null)
return;
Stack<object> stack = new Stack<object>();
BiTree p = tree;
do
{
while (p != null)
{
Console.WriteLine(p.Data);
stack.Push(p);
p = p.leftChild;
}
p = (BiTree)stack.Pop();
p = p.rightChild;
} while (stack.Count > 0 || p != null);
}
/// <summary>
/// 要用两个栈，比前两种复杂
/// </summary>
/// <param name="tree"></param>
public static void LastTravelStack(BiTree tree)
{
if (tree == null)
return;
//放访问过的节点
Stack<BiTree> stack1 = new Stack<BiTree>();
//放节点是否访问过 标志
Stack<bool> stackFlag = new Stack<bool>();
BiTree p=tree;
do
{
while (p != null)
{
stack1.Push(p);
stackFlag.Push(false);
p = p.leftChild;
}
p = stack1.Pop();
bool flag = stackFlag.Pop();
//第一次访问
if (!flag)
{
stack1.Push(p);
stackFlag.Push(true);
p = p.rightChild;
}//第二次访问
else
{
Console.WriteLine(p.Data);
p = null;
}
}
//栈不为空 或者 指针不为空
while (stack1.Count > 0 || p != null);
}
}