非递归遍历便利二叉树

来源：互联网发布：倚天指标源码编辑：程序博客网时间：2024/05/19 04:54
#include <iostream>#include <stack>using namespace std;struct TreeNode{    TreeNode* lChild;    TreeNode* rChild;    int m_iData;    TreeNode()    {        lChild = NULL;        rChild = NULL;        m_iData = 0;    }};/*递归实现前序遍历*/void PreOrder1(TreeNode* root){    if (root == NULL)    {        return ;    }    cout << "Data: " << root->m_iData << endl;    PreOrder1(root->lChild);    PreOrder1(root->rChild);}/*非递归，用栈实现1. 访问结点p之后，把p入栈，（是为了访问完左边，可以把这个根结点出栈来访问右结点)2. 判断结点P的左孩子是否为空，若为空，则取栈顶结点并进行出栈操作，并将栈顶结点的右孩子置为当前的结点P，循环至1);若不为空，则将P的左孩子置为当前的结点P;3. 直到P为NULL并且栈为空，则遍历结束。*/void PreOrder2(TreeNode* root){    stack<TreeNode*> S;    TreeNode* p = root;    while (p != NULL || !S.empty())    {        while (p != NULL)        {            cout << "Data: " << p->m_iData << endl;            S.push(p);            p = p->lChild;        }        if (!S.empty())        {            p = S.top();            S.pop();            p = p->rChild;        }    }}/*递归中序遍历*/void InOrder1(TreeNode* root){    if (root != NULL)    {        InOrder1(root->lChild);        cout << "Data: " << root->m_iData << endl;        InOrder1(root->rChild);    }}/*1. 若左孩子不为空，则将p入栈并将p的左孩子置为当前的p，然后对当前的p进行相同的处理2. 若其左孩子为空，则取栈顶元素并进行出栈操作，访问该栈顶元素，然后将当前的p置为栈顶的右孩子3. 直到p为NULL并且栈为空则遍历结束*/void InOrder2(TreeNode* root){    stack<TreeNode*> S;    TreeNode* p = root;    while (p != NULL || !S.empty())    {        while (p != NULL)        {            S.push(p);            p = p->lChild;        }        if (!S.empty())        {            p = S.top();            S.pop();            cout << "Data: " << p->m_iData << endl;            p = p->rChild;        }    }}/*递归后序遍历*/void PostOrder1(TreeNode* root){    if (root != NULL)    {        PostOrder1(root->lChild);        PostOrder1(root->rChild);        cout << "Data: " << root->m_iData << endl;    }}/*非递归实现：思路是这样的：当访问一个结点的时候，只有没有左结点也没有右结点或者都访问了的时候，才可以访问。*/void PostOrder2(TreeNode* root){    stack<TreeNode*> S;    TreeNode* cur = NULL;    TreeNode* pre = NULL;    S.push(root);    while (p != NULL || !S.empty())    {        cur = S.top();        if ((cur->lChild == NULL && cur->rChild == NULL)            || (pre != NULL && (pre == cur->lChild || pre == cur->rChild)))        {            cout << "Data: " << cur->m_iData << endl;            S.pop();            pre = cur;        }        else        {            if (cur->rChild != NULL)            {                S.push(cur->rChild);            }            if (cur->lChild != NULL)            {                S.push(cur->lChild);            }        }    }}int main(){    return 0;}
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