"Sword point offer" binary search tree to bidirectional linked list, C + + implementation

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# topics

Enter a binary search tree and convert the two-fork search tree into a sorted doubly linked list. Requires that no new nodes can be created, only the point pointer of the node in the tree can be adjusted. Requires that no new nodes can be created, only the pointer to the node in the tree is adjusted.

• Definition of binary tree node

  1/*  2 struct TreeNode {  3 int val;   4 struct TreeNode *left;   5 struct TreeNode *right;   6 TreeNode (int x):  7 val (x), left (null), right (null) {  8 }   9 }; */

• Example of binary search tree-to-doubly linked list

# ideas

• The nature of binary search tree
• Binary search tree is left sub-tree < root node < right subtree
• The middle sequence traversal of binary search tree is an ascending ordered sequence
• Thinking of binary search tree to bidirectional chain list
• The left pointer of the root node of the binary search tree points to the largest node of Zuozi, and the right subtree of the root node points to the smallest node of the right subtree.

# code

1 / * 2 struct TreeNode { 3 int val;  4 struct TreeNode *left; 5 struct TreeNode *right; 6 TreeNode (int x): 7 val (x), left (null), right (NULL) { 8 } 9};*/Ten classSolution { One  Public: Atreenode* Convert (treenode* prootoftree) -{/* The struct TreeNode  {int val,  TreeNode *left, and the  struct TreeNode *  Right TreeNode (int x): Val  (x), left (null), right (null) {};*/}      A classSolution { at  Public: -treenode* Convert (treenode* prootoftree) -{ -         //Bidirectional chain footer node -treenode* list_last = nullptr; -  in         //Recursive conversion -Convertnode (Prootoftree,list_last); to  +         //Doubly linked list first node -          while(List_last->left! = nullptr)//Boundary conditions the{ *List_last = list_last->left; $}Panax Notoginseng  -         //Return to the first node of the doubly linked list the         returnList_last; +} A  the     voidConvertnode (treenode* cur,treenode* list_last) +{ -         //Boundary conditions $         if(CUR==NULLPTR)return; $  -         //traverse the left subtree -         if(Cur->left! = nullptr) Convertnode (Cur->left,list_last); the  -         //Implement two-way link (establish connection)WuyiCur->left = List_last; the         if(List_last! = nullptr) list_last->right = cur; -List_last = cur; Wu  -         //Traverse Right sub-tree About         if(Cur->right! = nullptr) Convertnode (Cur->right,list_last); $} -}; -         if(Prootoftree = = NULL)returnNULL; -  ATreeNode *pointer = NULL; +  theConvert2list (prootoftree, pointer); -  $          while(Pointer->left!=null) the{ thepointer = pointer->left; the} the         returnPointer -} in     voidConvert2list (treenode* proot,treenode *&pointer) the{ the         if(Proot = = NULL) About{ the             return; the} the{ +             if(Proot->left! = NULL) -{ theConvert2list (Proot->left,pointer);Bayi} the  theProot->left = pointer; -             if(pointer! = NULL) -{ thePointer->right = Proot; the} the  thepointer = Proot; -             if(Proot->right!=null) the{ theConvert2list (proot->right, pointer); the}94} the} the};

"Sword point offer" binary search tree to bidirectional linked list, C + + implementation