二叉树的前序、中序、后序及层次遍历的递归与非递归源码实现

二叉树是基本却非常重要的数据结构，经常在面试中出现，现在我主要是针对面试中出现比率非常高的前序、中序、后序及层次遍历，给出自己的递归与非递归实现，源码仅供参考。
另外，如果觉得我写的好，可以关注我的github帐号(https://github.com/chenqiangzhishen). 本文代码部分我也贴在了如下的目录中。
(https://github.com/chenqiangzhishen/Algorithms/blob/master/binaryTree/binaryTree.c)
有了github，我会经常更新些新的，高效的，经典的算法和其他新的知识与大家分享，开源快乐～

注：我的代码不出意外，都可以直接运行，采用gcc/g++/gdb进行的开发与调试工具及vim开发工具。
因为比较喜欢在Linux下编程，不大喜欢用中文切来切去的进行描述，所以直接采用英文进行注释。

#include <stdio.h>#include <stdlib.h>#define MAX 100typedef struct BiTNode {    int data;    struct BiTNode *lchild, *rchild;} BiTNode, *BiTree;BiTNode* stack[MAX];BiTree createBiTree(void){    int data;    BiTNode *root = NULL;    scanf("%d", &data);    if(data == -1)    {        root = NULL;    }    else    {        root = (BiTNode *)malloc(sizeof(BiTNode));        root->data = data;        root->lchild = createBiTree();        root->rchild = createBiTree();    }    return root;}void preOrderTraverse(BiTree root){    if(root == NULL)        return;    printf("%d ", root->data);    preOrderTraverse(root->lchild);    preOrderTraverse(root->rchild);}void inOrderTraverse(BiTree root){    if(root == NULL)        return;    inOrderTraverse(root->lchild);    printf("%d ", root->data);    inOrderTraverse(root->rchild);}void postOrderTraverse(BiTree root){    if(root == NULL)        return;    postOrderTraverse(root->lchild);    postOrderTraverse(root->rchild);    printf("%d ", root->data);}void preOrderTraverse_none_recursive(BiTree root){    if(root == NULL)        return;    int top = 0;    while(root || top>0)    {        while(root)        {            printf("%d ", root->data);            stack[top++] = root;            root = root->lchild;        }        root = stack[--top];        root = root->rchild;    }    printf("\n");}void inOrderTraverse_none_recursive(BiTree root){    if(root == NULL)        return;    int top = 0;    while(root || top>0)    {        while(root)        {            stack[top++] = root;            root = root->lchild;        }        root = stack[--top];        printf("%d ", root->data);        root = root->rchild;    }    printf("\n");}void postOrderTraverse_none_recursive(BiTree root){    if(root == NULL)        return;    BiTNode *visited = NULL;    int top = 0;    while(root || top>0)    {        while(root)        {            stack[top++] = root;            root = root->lchild;        }        root = stack[top -1];        //if do not have right child or the right child is visited, then visit the parent(root) node.        if(root->rchild==NULL || visited==root->rchild)        {            printf("%d ", root->data);            visited = root;            --top;            root = NULL;//note that: let the node become NULL        }        else        {            root = root->rchild;        }    }    printf("\n");}void levelTraverse(BiTree root){    if(root == NULL)        return;    BiTNode* p = NULL;    int top = 0;    int beg = 0;    stack[top++] = root;    int end = top;    while(beg < end)    {        while(beg < end)        {            p = stack[beg++];            printf("%d ", p->data);            if(p->lchild)                stack[top++] = p->lchild;            if(p->rchild)                stack[top++] = p->rchild;        }        end = top;    }}int main(void){    printf("please input the data to create binary tree, input -1 to exit\n");    BiTree root = createBiTree();    printf("The binary tree is:\n");    printf("The preOrderTraverse is:\n");    preOrderTraverse(root);    printf("\n");    printf("The inOrderTraverse is:\n");    inOrderTraverse(root);    printf("\n");    printf("The postOrderTraverse is:\n");    postOrderTraverse(root);    printf("\n");    printf("The preOrderTraverse with none recursive is:\n");    preOrderTraverse_none_recursive(root);    printf("The inOrderTraverse with none recursive is:\n");    inOrderTraverse_none_recursive(root);    printf("The postOrderTraverse with none recursive is:\n");    postOrderTraverse_none_recursive(root);    printf("The level traverse for binary tree is:\n");    levelTraverse(root);    printf("\n");    return 0;}