二叉树前中后/层次遍历的递归与非递归形式（c++）

/*
二叉树前中后/层次遍历的递归与非递归形式
 */
//***************

void preOrder1(BinaryTreeNode* pRoot)
{
    if(pRoot==NULL)
       return;
    cout<<pRoot->value;
    if(pRoot->left!=NULL)
       preOrder1(pRoot->left);
    if(pRoot->right!=NULL)
       preOrder1(pRoot->right);
}

void preOrder2(BinaryTreeNode* pRoot)
{
    stack<BinaryTreeNode*> s;
    BinaryTreeNode *p=pRoot;
 
    if(pRoot==NULL)
        return;
    while(p!=NULL||!s.empty())
    {
       while(p!=NULL)
       {
           cout<<p->value<<" ";
           s.push(p);
           p=p->left;
       }
       if(!s.empty())
       {
           p=s.top();
           s.pop();
           p=p->right;
       }
    }
}

void preOrder2(BinaryTreeNode* pRoot){
   if(pRoot==NULL)
       return;
    stack<BinaryTreeNode*> s;  
    s.push(root);
    BinaryTreeNode* p;
    while(!s.empty()){
       p = s.top();
      cout<<p->data;//遍历根结点
        s.pop();
        if(p>right){
            s.push(p->right);  //先将右子树压栈
        }
        if(p->left){
            s.push(p->left);  //再将左子树压栈
        }
    }
}

//*****************

//中序遍历
void inOrder1(BinaryTreeNode* pRoot)
{
    if(pRoot==NULL)
        return;
    
    if(pRoot->left!=NULL)
        inOrder1(pRoot->left);
    cout<<pRoot->value;
    if(pRoot->right!=NULL)
        inOrder1(pRoot->right);
}

void inOrder2(BinaryTreeNode* pRoot)
{
    stack<BinaryTreeNode*> s;
    BinaryTreeNode *p=pRoot;
 
    if(pRoot==NULL)
        return;
    while(p!=NULL||!s.empty())
    {
       while(p!=NULL)
       { 
           s.push(p);
           p=p->left;
       }
       if(!s.empty())
       {
           p=s.top();
           cout<<p->value<<" ";
           s.pop();
           p=p->right;
       }
    }
}

//*****************

//后序遍历
void postOrder1(BinaryTreeNode* pRoot)
{
    if(pRoot==NULL)
        return;
    postOrder1(pRoot->left);
    postOrder1(pRoot->right);
    cout<<pRoot->value<<" ";
}

void postOrder2(BinaryTreeNode* pRoot)
{
    stack<BinaryTreeNode*> s;
    BinaryTreeNode *cur;
    BinaryTreeNode *pre=NULL;//记录上一个输出的节点
    s.push(pRoot);//根结点入栈
    while(!s.empty())
    {
        cur=s.top();
        if((cur->left==NULL&&cur->right==NULL)||(pre!=NULL&&(pre==cur->left||pre==cur->right)))
        {
            //左孩子和右孩子同时为空，或者当前结点的左孩子或右孩子已经遍历过了
            cout<<cur->value<<" ";
            s.pop();
            pre=cur;
        }
        else
        {
            if(cur->right!=NULL)
                s.push(cur->right);
            if(cur->left!=NULL)
                s.push(cur->left);
        }
    }
}

//*****************
//层次遍历，使用队列
void PrintFromTopToBottom(BinaryTreeNode* pRoot)
{
    if(pRoot == NULL)
        return;
 
    deque<BinaryTreeNode *> dequeTreeNode;
 
    dequeTreeNode.push_back(pRoot);
    while(dequeTreeNode.size())
    {
        BinaryTreeNode *pNode = dequeTreeNode.front();
        dequeTreeNode.pop_front();
         cout<<pNode->m_nValue<<" ";
        if(pNode->m_pLeft)
            dequeTreeNode.push_back(pNode->m_pLeft);
 
        if(pNode->m_pRight)
            dequeTreeNode.push_back(pNode->m_pRight);
    }
}


//深度优先遍历～先序遍历
void dfs(BinaryTreeNode* root){
    stack<BinaryTreeNode* *> nodeStack;  
    nodeStack.push(root);
    Node *node;
    while(!nodeStack.empty()){
       node = nodeStack.top();
      cout<<node->data;//遍历根结点
        nodeStack.pop();
        if(node->rchild){
            nodeStack.push(node->rchild);  //先将右子树压栈
        }
        if(node->lchild){
            nodeStack.push(node->lchild);  //再将左子树压栈
        }
    }
}
 
//广度优先遍历～层次遍历
void bfs(BinaryTreeNode* root){
    queue<BinaryTreeNode* *> nodeQueue;  
    nodeQueue.push(root);
    Node *node;
    while(!nodeQueue.empty()){
        node = nodeQueue.front();
        nodeQueue.pop();
        cout<<node->data;//遍历根结点
        if(node->lchild){
            nodeQueue.push(node->lchild);  //先将左子树入队
        }
        if(node->rchild){
            nodeQueue.push(node->rchild);  //再将右子树入队
        }
    }
}