Create 1669. Merge In Between Linked Lists

Author: Chayandas07

1669. Merge In Between Linked Lists

@@ -0,0 +1,37 @@
+/**
+ * Definition for singly-linked list.
+ * struct ListNode {
+ *     int val;
+ *     ListNode *next;
+ *     ListNode() : val(0), next(nullptr) {}
+ *     ListNode(int x) : val(x), next(nullptr) {}
+ *     ListNode(int x, ListNode *next) : val(x), next(next) {}
+ * };
+ */
+class Solution {
+public:
+    ListNode* mergeInBetween(ListNode* list1, int a, int b, ListNode* list2) {
+        ListNode* dummy = new ListNode();
+        dummy->next = list1;
+        
+        ListNode* prevA = dummy;
+        for (int i = 0; i < a; ++i) {
+            prevA = prevA->next;
+        }
+        
+        ListNode* prevB = prevA;
+        for (int i = a; i <= b + 1; ++i) {
+            prevB = prevB->next;
+        }
+        
+        ListNode* list2Tail = list2;
+        while (list2Tail->next != nullptr) {
+            list2Tail = list2Tail->next;
+        }
+        
+        prevA->next = list2;
+        list2Tail->next = prevB;
+        
+        return dummy->next;
+    }
+};