Create: 0092-reverse-linked-list-ii.cpp

gautham-8 · gautham-8 · commit 90437c0951a9 · 2023-03-02T18:28:57.000+05:30
diff --git a/cpp/0092-reverse-linked-list-ii.cpp b/cpp/0092-reverse-linked-list-ii.cpp
@@ -0,0 +1,34 @@
+/*
+    Given the head of a singly linked list and two integers left and right where left <= right, reverse the nodes of the list from position left to position right, and return the reversed list.
+    
+    Time complexity: O(n)
+    Space complexity: O(1)
+*/
+class Solution {
+public:
+    ListNode* reverseBetween(ListNode* head, int left, int right) {
+        ListNode* dummy = new ListNode();
+        dummy->next = head;
+
+        int i=0;
+        ListNode* leftConnector = dummy,*temp = head;
+        while(i<left-1){
+            leftConnector = temp;
+            temp = temp->next;
+            i++;
+        }
+        ListNode* prev = NULL;
+        i=0;
+        while(i<right-left+1){
+            ListNode* store = temp->next;
+            temp->next = prev;
+            prev = temp;
+            temp = store;
+            i++;
+        }
+        leftConnector->next->next = temp;
+        leftConnector->next = prev;
+
+        return dummy->next;
+    }
+};
