二元查找树转为双向链表

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。要求不能创建任何新的结点，只调整指针的指向。 
　　比如将二元查找树 
                                             10 
                                           /      / 
                                         6       14 
                                      /   /    /　 / 
                                    4     8  12  16 
转换成双向链表 。
4=6=8=10=12=14=16。 

声明：思想不是原创。

方法一：其思想是分别转换左右子树成双向链，再通过根节点进行连接

#include <iostream> using namespace std; struct BSTree { int num; BSTree* left; BSTree* right; }; BSTree *convertToLink(BSTree *tree,bool asRight) { BSTree *pleft=0;//节点tree的左子树转换成的双向链表 BSTree *pright=0;//节点tree的右子树转换成的双向链表 //如果左子树不为空，则先转换左子树 if(tree->left) pleft=convertToLink(tree->left,false); //如果双向左链表不为空，将此节点加到末尾 if(pleft) { pleft->right=tree; tree->left=pleft; } if(tree->right) pright=convertToLink(tree->right,true); if(pright) { pright->left=tree; tree->right=pright; } BSTree *pTemp=tree; //如果当前节点tree为其根节点的右子树，则返回此树的最小节点，即为父节点的右子链表的最左节点 if(asRight) { while(pTemp->left) pTemp=pTemp->left; } //否则返回最大节点，相当于父节点左子链表的最右节点 else { while(pTemp->right) pTemp=pTemp->right; } return pTemp; } void main() { BSTree *root; BSTree *p4 = new BSTree(); p4->num=4; BSTree *p8 = new BSTree(); p8->num=8; BSTree *p6 = new BSTree(); p6->num=6; p6->left=p4; p6->right=p8; BSTree *p12 = new BSTree(); p12->num=12; BSTree *p14 = new BSTree(); p14->num=14; p14->left=p12; BSTree *p10 = new BSTree(); p10->num=10; p10->left=p6; p10->right=p14; root = p10; root=convertToLink(root,true); cout<<root->num<<"="; while(root->right){ root=root->right; cout<<root->num<<"="; } cin.get(); }

方法二：更容易理解，中序遍历树，那依次访问的节点本身就是有序的，将节点依次加入到链表末尾即可

#include <iostream> using namespace std; struct BSTree { int num; BSTree* left; BSTree* right; }; /** 中序遍历二元查找树，将节点依次加入到双向链表末尾 **/ void convertToLink2(BSTree *tree,BSTree *&lastNodeInList) { if(tree->left) convertToLink2(tree->left,lastNodeInList); if(lastNodeInList) { lastNodeInList->right=tree; tree->left=lastNodeInList; lastNodeInList=tree; } else { lastNodeInList=tree; } if(tree->right) convertToLink2(tree->right,lastNodeInList); } void main() { BSTree *root; BSTree *p4 = new BSTree(); p4->num=4; BSTree *p8 = new BSTree(); p8->num=8; BSTree *p6 = new BSTree(); p6->num=6; p6->left=p4; p6->right=p8; BSTree *p12 = new BSTree(); p12->num=12; BSTree *p14 = new BSTree(); p14->num=14; p14->left=p12; BSTree *p10 = new BSTree(); p10->num=10; p10->left=p6; p10->right=p14; root = p10; //root=convertToLink(root,true); //cout<<root->num<<"="; //while(root->right){ // root=root->right; // cout<<root->num<<"="; //} BSTree *doubleLink=NULL; convertToLink2(root,doubleLink); while(doubleLink->left) doubleLink=doubleLink->left; cout<<doubleLink->num; while(doubleLink->right) { doubleLink=doubleLink->right; cout<<"="<<doubleLink->num; } cin.get(); }