关于二叉树的生成, 遍历 在线求指导!该如何处理

关于二叉树的生成, 遍历 在线求指导!
为什么下面的程序运行时, 进行遍历操作, 会出现指针越界呢?

我还以为二叉树的应用很简单, 但是, 因为这个遍历, 我已经烦恼了2个小时了...

C/C++ code

#include <iostream>using namespace std;const int queueSize = 100; //层序遍历所用的队列的最大度struct biNode //用结构体定义二叉树{    char word;    biNode *lchild, *rchild; };biNode *creat(biNode *node) //生成二叉树{    cout<<"请输入节点\n (输入数字 0 , 即结束节点输入\n";    char word;                 cin>>word;    if (word == '0')        return NULL;   //结束子树    else    {        node = new biNode;         node->word = word;        node->lchild = creat(node);        node->rchild = creat(node);    }}biNode *setup(biNode *root) {    biNode *go; //执行节点    go = new biNode;    cout<<"请输入根节点\n ";    cin>>go->word;    root = go;    creat(go);  //递归生成二叉树    return root;}void preOrder(biNode *root) //前序遍历{    if (root != NULL)    {        cout<<root->word<<" ";        preOrder(root->lchild);         preOrder(root->rchild);    }}void inOrder(biNode *root) //中序遍历{    if (root != NULL)    {        inOrder(root->lchild);        cout<<root->word<<" ";        inOrder(root->rchild);    }}void postOrder(biNode *root) //后续遍历{    if (root != NULL)    {        postOrder(root->lchild);        postOrder(root->rchild);        cout<<root->word<<" ";    }}void levelOrder(biNode *root) //层序遍历{    biNode *queue[queueSize];    biNode *q;    int front, rear;    front = rear = -1;    if (root == NULL)        return ;    queue[++rear] = root;    while (front != rear)    {        q = queue[++front];        cout<<q->word;        if (q->lchild != NULL)             queue[++rear] = q->lchild;        if (q->rchild != NULL)            queue[++rear] = q->rchild;    }}        int main(){        biNode *root, *go;    root = go = NULL; //初始化    while(1)    {        cout<<"\t\t二叉树, 二叉树, 二叉树!\n\n";        cout<<"1, 生成二叉树\n";        cout<<"2, 前序遍历\n";        cout<<"3, 中序遍历\n";        cout<<"4, 后续遍历\n";        cout<<"5, 程序遍历\n";        cout<<"6, 退出\n";        cout<<"输入 1 到 6 的数字, 选择相应功能\n";        int judge;        cin>>judge;        switch (judge)        {        case 1:            {                root = setup(go);                break;            }        case 2:            {                cout<<"前序遍历:\n";                preOrder(root);                break;            }        case 3:            {                cout<<"中序遍历:\n";                inOrder(root);                break;            }        case 4:            {                cout<<"后续遍历:\n";                postOrder(root);                break;            }        case 5:            {                cout<<"层序遍历:\n";                levelOrder(root);                break;            }        case 6:            {                exit(1);            }        default:            {                cout<<"Please enter a number from 1 to 6!\n";                break;            }        }    }    return 0;}

C/C++ code

        node->lchild = creat(node);node->rchild = creat(node);