100题_01 把二元查找树转变成排序的双向链表

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。分析：可以采用递归的思想，先将左子树转成双向列表，再将右子树转成双向列表，最后将这两个双向列表及根结点组首尾相接，组合成一个双向列表。以下是实现的代码： BSTreeNode.h

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#pragma once #include <cstdlib> using namespace std; class BSTree; class BSTreeNode { friend class BSTree; public: BSTreeNode(int data, BSTreeNode *rc = NULL, BSTreeNode *lc = NULL); private: int data; BSTreeNode *rc; BSTreeNode *lc; };

BSTreeNode.cpp

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#include "BSTreeNode.h" BSTreeNode::BSTreeNode(int data, BSTreeNode *rc, BSTreeNode *lc) { this->data = data; this->lc = lc; this->rc = rc; }

BSTree.h

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#pragma once #include "BSTreeNode.h" class BSTree { public: BSTree(void); ~BSTree(void); void insert(int data); void convertToDoubleList(); private: BSTreeNode* root; void del(BSTreeNode* node); BSTreeNode* convertToDoubleList(BSTreeNode *&node); };

BSTree.cpp

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#include "BSTree.h" #include <cstdlib> using namespace std; BSTree::BSTree(void) { root = NULL; } void BSTree::insert(int data) { if (root == NULL) { root = new BSTreeNode(data); } else { BSTreeNode *cur, *pre; pre = NULL; cur = root; while (true) { pre = cur; if (cur->data <= data) { cur = cur->rc; if (!cur) { pre->rc = new BSTreeNode(data); break; } } else { cur = cur->lc; if (!cur) { pre->lc = new BSTreeNode(data); break; } } } } } BSTree::~BSTree(void) { } void BSTree::del(BSTreeNode *node) { if (node == NULL) return; del(node->lc); del(node->rc); delete node; root = NULL; } BSTreeNode* BSTree::convertToDoubleList(BSTreeNode*& node) { if (node == NULL) return NULL; BSTreeNode *lf, *lt, *rf, *rt, *f, *t; lf = node->lc; rf = node->rc; lt = convertToDoubleList(lf); rt = convertToDoubleList(rf); if (lt != NULL) { lt->rc = node; f = lf; } else f = node; node->lc = lt; node->rc = rf; if (rf != NULL) { rf->lc = node; t = rt; } else t = node; node = f; return t; } void BSTree::convertToDoubleList() { convertToDoubleList(root); }

main.cpp

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#include <iostream> #include "BSTree.h" using namespace std; int main() { BSTree tr; tr.insert(10); tr.insert(7); tr.insert(8); tr.insert(52); tr.convertToDoubleList(); return 0; }