二叉查找树转双向链表

将一个二叉查找树转换成排好序的双向链表，不能创建中间节点，只能调整节点的指向

struct Node{int value;Node* left;Node* right;Node(int value){this->value = value;left = NULL;right = NULL;}};struct HeadTail{Node* head;Node* tail;HeadTail(){head = NULL;tail = NULL;}};HeadTail convert(Node* root){HeadTail result;if (root == NULL)return result;result.head = root;result.tail = root;if (root->left != NULL){HeadTail leftResult = convert(root->left);  root->left = leftResult.tail;      //将当前根节点的left指向左子树的链表尾leftResult.tail->right = root;     //将左子树的链表尾的right指向当前根节点result.head = leftResult.head;     //将返回结果中的链表头更新为左子树的链表头}if (root->right != NULL){HeadTail rightResult = convert(root->right);root->right = rightResult.head;    //同上rightResult.head->left = root;result.tail = rightResult.tail;}return result;}