Create convert-binary-search-tree-to-sorted-doubly-linked-list.cpp

Author: kamyu104

C++/convert-binary-search-tree-to-sorted-doubly-linked-list.cpp

@@ -0,0 +1,42 @@
+// Time:  O(n)
+// Space: O(h)
+
+/*
+// Definition for a Node.
+class Node {
+public:
+    int val;
+    Node* left;
+    Node* right;
+
+    Node() {}
+
+    Node(int _val, Node* _left, Node* _right) {
+        val = _val;
+        left = _left;
+        right = _right;
+    }
+};
+*/
+class Solution {
+public:
+    Node* treeToDoublyList(Node* root) {
+        if (!root) {
+            return nullptr;
+        }
+        Node *left_head = root, *left_tail = root;
+        Node *right_head = root, *right_tail = root;
+        if (root->left) {
+            left_head = treeToDoublyList(root->left);
+            left_tail = left_head->left;
+        }
+        if (root->right) {
+            right_head = treeToDoublyList(root->right);
+            right_tail = right_head->left;
+        }
+        left_tail->right = root, right_head->left = root;
+        root->left = left_tail, root->right = right_head;
+        left_head->left = right_tail, right_tail->right = left_head;
+        return left_head;
+    }
+};