不多说了,又是忘掉了这个东西,手动扣点代码,找找感觉
二叉查找树,首先,它得是棵树,对吧,而且还是个二叉树对吧,大体长这个样子
呃呃,为了后面省事,这张直接给出了平衡二叉树,那个是一种特殊的二叉查找树,后续会撸源码,这次只说二叉查找树。好的,回到上面的树,首先这棵树是由各个节点组成的(这不废话),然后每个节点只有两个出度,分别为左孩子以及右孩子(两个指针,指向相同的节点),还有一个重要的性质是,对于某一节点其左子树上的所有节点全部小于它的值,其右子树上的所有节点值全部都大于其值,其定义如下:
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struct Node{
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struct Node *left;
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struct Node *right;
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int val;
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Node(int x):val(x), left(NULL), right(NULL){}
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};
只有这一个结构只能保证有左右两个孩子,不能保证数值大小的性质,这就要在我们插入的时候费点心思了,代码如下(
注:我是把该树建了一个类,第一段代码时.h文件,所有操作在里面完成,后面不再赘述):
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#ifndef BSTTREE_H
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#define BSTTREE_H
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#include <iostream>
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#include <stack>
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struct Node{
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struct Node *left;
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struct Node *right;
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int val;
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Node(int x):val(x), left(NULL), right(NULL){}
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};
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class BSTTree
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{
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public:
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BSTTree();
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~BSTTree();
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void preOrderWithRecur(struct Node *node);
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void preOrderNon_Recur(struct Node *node);
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void inOrderWithRecur(struct Node *node);
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void inOrderNon_Recur(struct Node *node);
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void postOrderWithRecur(struct Node *node);
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void postOrderNon_Recur(struct Node *node);
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bool isExist(struct Node *node, int k);
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bool insert(struct Node *node, int k);
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int getHeight(struct Node *node);
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bool delNode(struct Node *node, int k);
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struct Node *root;
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private:
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bool delRoot();
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bool delNodeLeftNULL(struct Node *parent, struct Node *node);
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bool delNodeRightNULL(struct Node *parent, struct Node *node);
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bool delRootLeftNULL();
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bool delRootRightNULL();
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};
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#endif // BSTTREE_H
插入代码如下,过程就是从根找起,直到找到自己的位置~~~
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bool BSTTree::isExist(Node *node, int k){
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struct Node *p = node;
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while(p){
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if(p->val == k) return true;
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else if(p->val > k) p = p->left;
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else p = p->right;
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}
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return false;
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}
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bool BSTTree::insert(struct Node *node, int k){
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if(isExist(node, k))
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return false;
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struct Node *p = node, *parent = NULL;
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while(p){
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parent = p;
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if(p->val > k) p = p->left;
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else p = p->right;
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}
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p = new struct Node(k);
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if(root == NULL){ root = p; return true;}
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else if(parent->val > p->val) parent->left = p;
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else parent->right = p;
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return true;
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}
这里特殊情况就是在树为空的时候,要判断一下(因为那时候祖宗还没出现。。。)
接下来讲一下删除,相信大家通过.h文件已经了解到,我是分了好多情况进行讨论来实现的,(因为自己实力有限,看着各种嵌套有点乱)总体来讲,分成两个部分,一个是删除根节点,一个是删除非根节点,因为如果删除非根节点的话,就需要知道其父节点信息,所以分了一下,再有就是在这两大类下面又各自分了两类--->左子树为空,右子树为空,具体代码如下:
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bool BSTTree::delNode(struct Node *node, int k){
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struct Node *parent, *child;
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if(root == NULL) return false;
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if(root->val == k) return delRoot();
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node = root;
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while(node){
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if(node->val == k) break;
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parent = node;
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if(node->val > k) node = node->left;
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else node = node->right;
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}
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if(node == NULL) return false;
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if(node->left== NULL && node->right == NULL){
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if(node == parent->left) parent->left = NULL;
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else parent->right = NULL;
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delete node;
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node = NULL;
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return true;
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}else if(node->left==NULL)
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return delNodeLeftNULL(parent, node);
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else if(node->right== NULL)
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return delNodeRightNULL(parent, node);
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else{
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parent = node, child = node->right;
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int temp;
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while(child->left){ parent = child; child = child->left;}
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temp=node->val; node->val = child->val; child->val = temp;
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if(child == parent->left) parent->left = child->right;
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else parent->right = child->right;
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delete child, child = NULL;
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return true;
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}
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}
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bool BSTTree::delNodeLeftNULL(struct Node *parent, struct Node *node){
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if(parent->left == node) parent->left = node->right;
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else parent->right = node->right;
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delete node;
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node = NULL;
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return true;
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}
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bool BSTTree::delNodeRightNULL(struct Node *parent, struct Node *node){
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if(parent->left == node) parent->left = node->left;
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else parent->right = node->left;
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delete node;
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node = NULL;
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return true;
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}
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bool BSTTree::delRoot(){
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if(root->left == NULL && root->right == NULL){
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delete root;
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root = NULL;
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return true;
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}else if(root->left == NULL){
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return delRootLeftNULL();
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}else if(root->right == NULL){
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return delRootRightNULL();
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}else{
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struct Node *parent = root, *child = root->right;
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int temp;
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while(child->left){ parent = child; child = child->left;}
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temp = root->val; root->val = child->val; child->val = temp;
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if(child == parent->left) parent->left = child->right;
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else parent->right = child->right;
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delete child;
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child = NULL;
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return true;
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}
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}
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bool BSTTree::delRootLeftNULL(){
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struct Node *p = root;
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root = root->right;
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delete p;
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return true;
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}
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bool BSTTree::delRootRightNULL(){
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struct Node *p = root;
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root = root->left;
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delete p;
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return true;
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}
当左右子树都为空的时候,直接删除就行,但是要注意父节点的指针置为NULL,要不然就是野指针了,知道什么奇奇怪怪的东西就不太好了~~~左(右)子树为空时直接将父节点指针指向对应右(左)子树即可,然后删除节点,至于左右子树都为非空,则需要找到右子树的后继,然后调换数值,后续就按照删除一个左子树为空的节点即可,几种情况分别如下图所示,只列举了右子树为空的情况,其中parent表示被删除节点的父节点指针,child表示要删除节点指针:
左右都为空:
右为空:
左右均非空:
接下直接上遍历代码了,包括递归和非递归的,非递归要借助栈来实现,剩下的感觉只要理解中序遍历就行了,剩下两个都是在它的基础上改了一点:
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void BSTTree::preOrderWithRecur(struct Node *node){
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if(node){
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std::cout<< node->val<<" ";
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preOrderWithRecur(node->left);
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preOrderWithRecur(node->right);
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}
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}
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void BSTTree::inOrderWithRecur(struct Node *node){
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if(node){
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inOrderWithRecur(node->left);
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std::cout<<node->val<<" ";
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inOrderWithRecur(node->right);
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}
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}
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void BSTTree::postOrderWithRecur(struct Node *node){
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if(node){
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postOrderWithRecur(node->left);
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postOrderWithRecur(node->right);
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std::cout<<node->val<<" ";
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}
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}
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void BSTTree::preOrderNon_Recur(struct Node *node){
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std::stack<struct Node*> s;
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struct Node *p = node;
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while(p || !s.empty()){
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while(p){
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std::cout<<p->val<<" ";
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s.push(p);
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p=p->left;
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}
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p = s.top(), s.pop();
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if(p->right) p = p->right;
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else p = NULL;
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}
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}
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void BSTTree::inOrderNon_Recur(struct Node *node){
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std::stack<struct Node*> s;
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struct Node *p = node;
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while(p || !s.empty()){
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while(p){
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s.push(p);
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p=p->left;
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}
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p = s.top(), s.pop();
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std::cout<<p->val<<" ";
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if(p->right) p = p->right;
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else p = NULL;
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}
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}
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void BSTTree::postOrderNon_Recur(struct Node *node){
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std::stack<struct Node*> s;
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struct Node *p = node;
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while(p || !s.empty()){
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while(p){
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s.push(p);
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p=p->left;
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}
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p = s.top(), s.pop();
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std::cout<<p->val<<" ";
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if(!s.empty() && p == s.top()->left) p = s.top()->right;
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else p = NULL;
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}
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}
还请各位看官老爷多提宝贵意见~~~
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