二叉树的建立（多种方法）

非递归实现

typedef struct BiTNode{
char data;
BiTNode* lchild, *rchild;
}BiTree;

//非递归实现二叉树的建立
BiTree* BiTreeCreate(){
BiTree* Q[100];
char ch;
int front, rear;
BiTree* s, *root;
root = NULL;
front = 1;
rear = 0;
cout << "请完全按照二叉树的编号顺序输入节点序列：" << endl;
cout << "空节点用@表示，输入序列以#结束" << endl;
ch = getchar();
while (ch != '#')
{
s = NULL;
if (ch != '@')
{
s = new BiTree();
s->data = ch;
s->lchild = NULL;
s->rchild = NULL;
}
rear++;
//这儿无论节点是否为空都放入数组
Q[rear] = s;
if (rear == 1)
root = s;
else
{
//若此节点为空则不需要对根节点的左右孩子赋值，因为创立节点时就把左右孩子节点默认为空
if (s != NULL&&Q[front] != NULL)
{
if (rear % 2 == 0)//rear为偶数，说明此节点为根节点的左子树
Q[front]->lchild = s;
else//rear为奇数，说明此节点为根节点的右子树
Q[front]->rchild = s;
}
//rear为奇数，说明一颗最基本二叉树（根，左右孩子）完成
//此时使front+1,指向数组中下一位元素，进行它的二叉树建立
if (rear % 2 == 1)
{
front++;
}
}

ch = getchar();
}

return root;
}

递归实现：
struct tree{
int data;
tree* lchild, *rchild;
};

void BTree::create(tree* &s){
int n;
cin >> n;
if (n == 0)
s = NULL;
else{
s = new tree();
s->data = n;
/*BTree类中的root
if (root == NULL)
root = s;
*/
create(s->lchild);
create(s->rchild);
}
}

void BTree::Build(int x,tree* &bt){
bt = new tree();
bt->data = x;
if (root == NULL)
root = bt;
cout << x << " left child is";
cin >> x;
if (x != 0){
cout << "进入" << bt->data << "这个节点的左子树建设" << endl;
Build(x, bt->lchild);
}
else{
cout << bt->data << "左子树为空,即将返回上层" << endl;
bt->lchild = NULL;
}
cout << bt->data<< " right child is";
cin >> x;
if (x != 0){
cout << "进入" << bt->data << "这个节点的右子树建设" << endl;
Build(x, bt->rchild);
}
else{
cout << bt->data << "右子树为空,即将返回上层" << endl;
bt->rchild = NULL;
}

return ;
}