把二元查找树转变成排序的双向链表

把二元查找树转变成排序的双向链表

 题目：

输入一棵二元查找树，将该二元查找树转换成一个排序的双向链表。

  10
  / /
 6 14
 / / / /
4 8 12 16
   
 转换成双向链表
4=6=8=10=12=14=16。
   
 首先我们定义的二元查找树节点的数据结构如下：
 struct BSTreeNode
{
  int m_nValue; // value of node
  BSTreeNode *m_pLeft; // left child of node
  BSTreeNode *m_pRight; // right child of node

};

主函数如下：

#include <iostream>#include "BST.h"using namespace std;//将二元查找树转变成双向链表int main(){int data[]={10,6,14,4,8,12,16};int num=7;struct BSTreeNode *Root=NULL;BSTree tp1;struct ListNode *lroot;//二元查找树的建立Root=tp1.buildBSTree(Root,data,num);    //显示std::cout<<"前序遍历:"<<std::endl;tp1.BSTreeNodePrint_midfirst(Root);std::cout<<"中序遍历:"<<std::endl;tp1.BSTreeNodePrint_leftfirst(Root);std::cout<<"后序遍历:"<<std::endl;tp1.BSTreeNodePrint_rightfirst(Root);//按中序遍历的顺序将二元查找树转换成双向链表lroot=BSTreeToList(Root);//显示链表中的内容std::cout<<"链表显示："<<std::endl;ListNodePrint(lroot);return 1;}

BST.h

#ifndef _BST_H_#define _BST_H_#include <iostream>struct BSTreeNode{int m_nValue; // value of nodeBSTreeNode *m_pLeft; // left child of nodeBSTreeNode *m_pRight; // right child of node};struct ListNode{int data;ListNode *m_left;ListNode *m_right;};class BSTree{public:BSTreeNode *buildBSTree(BSTreeNode *root,int *data,int num);BSTreeNode *BSTreeDelete(BSTreeNode *root,int *data,int num);void BSTreeNodePrint_leftfirst(BSTreeNode *root);void BSTreeNodePrint_midfirst(BSTreeNode *root);void BSTreeNodePrint_rightfirst(BSTreeNode *root);};struct ListNode *BSTreeToList(BSTreeNode *root);void BSTreeListSearch(BSTreeNode *root,ListNode **lroot,ListNode **currentListNode,int &m);void ListNodePrint(ListNode *head);#endif

BST.cpp

#include "BST.h"BSTreeNode *BSTree::buildBSTree(BSTreeNode *root,int *data,int num){for(int i=0;i<num;i++){BSTreeNode *z=(struct BSTreeNode*)malloc(sizeof(struct BSTreeNode));//结构体指针需要初始化z->m_nValue=*(data+i);//initialize new nodez->m_pLeft=NULL;z->m_pRight=NULL;BSTreeNode *y=NULL;BSTreeNode *x=root;while(x!=NULL){y=x;if (z->m_nValue<x->m_nValue){x=x->m_pLeft;}else{x=x->m_pRight;}}if (y==NULL){root=z;}else if (z->m_nValue<y->m_nValue){y->m_pLeft=z;}else{y->m_pRight=z;}}return root;}void BSTreeListSearch(BSTreeNode *root,ListNode **lroot,ListNode **currentListNode,int &m)//{BSTreeNode *currentNode=root;if(root!=NULL){ListNode *zp=(struct ListNode*)malloc(sizeof(struct ListNode));if (currentNode->m_pLeft!=NULL){BSTreeListSearch(currentNode->m_pLeft,lroot,currentListNode,m);}m++;//通过m判断是否为双向链表的第一个元素//将该节点加入到链表中zp->data=currentNode->m_nValue;zp->m_left=*currentListNode;zp->m_right=NULL;if (m!=1){(*currentListNode)->m_right=zp;}//更新链表中当前节点*currentListNode=zp;if(m==1){*lroot=*currentListNode;}if (currentNode->m_pRight!=NULL){BSTreeListSearch(currentNode->m_pRight,lroot,currentListNode,m);}}}struct ListNode *BSTreeToList(BSTreeNode *root){ListNode *P=NULL;ListNode *Q=NULL;//保证链表头结点的左向指针为空ListNode **currentListNode=&Q;ListNode **lroot=&P;int m=0;BSTreeListSearch(root,lroot,currentListNode,m);return *lroot;}void ListNodePrint(ListNode *head){while(head !=NULL){std::cout<<head->data<<std::endl;head=head->m_right;}}void BSTree::BSTreeNodePrint_leftfirst(BSTreeNode *root)//左根右，中序遍历{BSTreeNode *currentNode=root;if(root!=NULL){if (currentNode->m_pLeft!=NULL){BSTreeNodePrint_leftfirst(currentNode->m_pLeft);}std::cout<<currentNode->m_nValue<<std::endl;if (currentNode->m_pRight!=NULL){BSTreeNodePrint_leftfirst(currentNode->m_pRight);}}}void BSTree::BSTreeNodePrint_midfirst(BSTreeNode *root)//根左右，前序遍历{BSTreeNode *currentNode=root;if(currentNode!=NULL){std::cout<<currentNode->m_nValue<<std::endl;}if (currentNode->m_pLeft!=NULL){BSTreeNodePrint_midfirst(currentNode->m_pLeft);}if (currentNode->m_pRight!=NULL){BSTreeNodePrint_midfirst(currentNode->m_pRight);}}void BSTree::BSTreeNodePrint_rightfirst(BSTreeNode *root)//左右根，后序遍历{BSTreeNode *currentNode=root;if (root!=NULL){if (currentNode->m_pLeft!=NULL){BSTreeNodePrint_rightfirst(currentNode->m_pLeft);}if (currentNode->m_pRight!=NULL){BSTreeNodePrint_rightfirst(currentNode->m_pRight);}std::cout<<currentNode->m_nValue<<std::endl;}}

运行结果：