二叉树遍历非递归的代码

二叉树遍历的递归代码比较简单，但非递归遍历就稍微复杂些，需要用栈来存储遍历过的节点。

下面给出代码。

// 二叉树定义typedef struct BiTnode{char data;struct BiTnode *lchild, *rchild;}BiTnode, *BiTree;// 栈节点定义typedef struct SNode{BiTree elem;struct SNode* next;}SNode;// 带标志位的栈节点定义，用于后序遍历typedef struct SNodeF {BiTree elem;short flag;struct SNodeF* next;}SNodeF;  

PS. 二叉树和栈的定义都是按照《软件设计师教程第二版》上来写的，非常粗糙和恶心。如果能强忍着看完该书上的代码，那你再看其它的垃圾代码都不会反胃了。

 void PreOrder_stack(BiTree root){SNode *stacktop = NULL;stacktop = new SNode;stacktop->elem = root;stacktop->next = NULL;while (stacktop != NULL){SNode *sp = stacktop;stacktop = stacktop->next;cout << sp->elem->data << endl;if (NULL != sp->elem->rchild){SNode *pNode = new SNode;pNode->elem = sp->elem->rchild;pNode->next = stacktop;stacktop = pNode;}if (NULL != sp->elem->lchild){SNode *pNode = new SNode;pNode->elem = sp->elem->lchild;pNode->next = stacktop;stacktop = pNode;}delete sp;}}void InOrder_stack(BiTree root){SNode *stacktop = NULL;BiTree btp = root;while (btp != NULL || stacktop != NULL){if (btp != NULL){SNode *pNode = new SNode;pNode->next = stacktop;pNode->elem = btp;stacktop = pNode;btp = btp->lchild;}else{SNode *pNode = stacktop;stacktop = stacktop->next;cout << pNode->elem->data << endl;btp = pNode->elem->rchild;delete pNode;}}}void PostOrder_stack(BiTree root){SNodeF *stacktop = new SNodeF;stacktop->elem = root;stacktop->flag = 2;stacktop->next = NULL;while (stacktop != NULL){if (stacktop->elem->lchild == NULL && stacktop->elem->rchild == NULL){cout << stacktop->elem->data << endl;SNodeF *pNode = stacktop;stacktop = stacktop->next;delete pNode;}if (stacktop->flag == 2 && stacktop->elem->lchild != NULL){SNodeF *pNode = new SNodeF;pNode->elem = stacktop->elem->lchild;pNode->flag = 2;pNode->next = stacktop;stacktop->flag = 1;stacktop = pNode;continue;}else if (stacktop->flag == 1 && stacktop->elem->rchild != NULL){SNodeF *pNode = new SNodeF;pNode->elem = stacktop->elem->rchild;pNode->flag = 2;pNode->next = stacktop;stacktop->flag = 0;stacktop = pNode;continue;}else if (stacktop->flag == 0){cout << stacktop->elem->data << endl;SNodeF *pNode = stacktop;stacktop = stacktop->next;delete pNode;}}}