feat:add Solution.cpp for 0114. Flatten Binary Tree to Linked List

Author: Stackingrule

solution/0100-0199/0114.Flatten Binary Tree to Linked List/Solution.cpp

@@ -0,0 +1,16 @@
+class Solution {
+public:
+    void flatten(TreeNode* root) {
+        TreeNode* cur = root;
+        while (cur) {
+            if (cur->left) {
+                TreeNode* p = cur->left;
+                while (p->right) p = p->right;
+                p->right = cur->right;
+                cur->right = cur->left;
+                cur->left = nullptr;
+            }
+            cur = cur->right;
+        }
+    }
+};