C语言非递归实现二叉树的先序、中序、后序、层序遍历

#include <stdio.h>    
#include <stdlib.h>  
#include <stack>
#include <queue>
using namespace std;

//*****二叉树的二叉链表存储表示*****//    
typedef struct BiNode    
{    
    char data;    
    struct BiNode *lchild, *rchild; 
    int visitCount;
}BiNode, *BiTree;   

//*****按先序次序输入二叉树中结点的值(一个字符)，空格字符表示空树构造二叉链表表示的二叉树T*****//    
void CreateBiTree(BiTree &T)            
{                                      
    char ch;    
    scanf("%c", &ch);    
    if(ch == ' ')    
    {    
        T = NULL;    
    }    
    else    
    {    
        if(!(T = (BiNode *)malloc(sizeof(BiNode))))    
        {    
            return;    
        }    
        T->data = ch;                            //生成根结点    
        T->lchild = NULL;
        T->rchild = NULL;
        CreateBiTree(T->lchild);                //构造左子树    
        CreateBiTree(T->rchild);                //构造右子树    
    }   

    return;    
}   

//*****先序遍历二叉树*****//    
void PreOrderTraverse(BiTree T)    
{    
    stack<BiTree> TreeStack;
    BiTree p = T;

    while (p || !TreeStack.empty())
    {
        if (p)
        {
            printf("%c ", p->data);
            TreeStack.push(p);
            p = p->lchild;
        }
        else
        {
            p = TreeStack.top();
            TreeStack.pop();
            p = p->rchild;
        }
    }
}   

//*****中序遍历二叉树*****//    
void InOrderTraverse(BiTree T)    
{    
    stack<BiTree> TreeStack;
    BiTree p = T;

    while (p || !TreeStack.empty())
    {
        if (p)
        {
            TreeStack.push(p);
            p = p->lchild;
        }
        else
        {
            p = TreeStack.top();
            printf("%c ", p->data);
            TreeStack.pop();
            p = p->rchild;
        }
    }
}   

//*****后序遍历二叉树*****//    
void PostOrderTraverse(BiTree T)    
{    
    stack<BiTree> TreeStack;
    BiTree p = T;

    while (p || !TreeStack.empty())
    {
        if (p)
        {
            p->visitCount = 1;
            TreeStack.push(p);
            p = p->lchild;
        }
        else
        {
            p = TreeStack.top();
            TreeStack.pop();
            if (p->visitCount == 2)
            {
                printf("%c ", p->data);
                p = NULL;
            }
            else
            {
                p->visitCount++;
                TreeStack.push(p);
                p = p->rchild;
            }
        }
    }
} 

//*****层序遍历二叉树*****// 
void LevelOrderTraverse(BiTree T)
{
    if (!T)
    {
        return;
    }

    queue<BiTree> TreeQueue;
    TreeQueue.push(T);
    BiTree p = T;
    while (!TreeQueue.empty())
    {
        p = TreeQueue.front();
        TreeQueue.pop();
        printf("%c ", p->data);

        if (p->lchild)
        {
            TreeQueue.push(p->lchild);
        }
        if (p->rchild)
        {
            TreeQueue.push(p->rchild);
        }
    }
}

int main(void)    
{    
    BiTree T;        
    printf("请按先序次序输入二叉树中结点的值(字符)，空格字符表示空树:\n");    
    CreateBiTree(T);       

    printf("先序遍历结果为:");    
    PreOrderTraverse(T);    
    printf("\n\n");   

    printf("中序遍历结果为:");    
    InOrderTraverse(T);    
    printf("\n\n");   

    printf("后序遍历结果为:");    
    PostOrderTraverse(T);        
    printf("\n\n");     

    printf("层序遍历结果为:");    
    LevelOrderTraverse(T);        
    printf("\n\n");

    return 0;        
}

原文地址：http://www.linuxidc.com/Linux/2015-02/113460.htm