Create 092.Reverse-Linked-List-II_v2.cpp

Author: wisdompeak

Linked_List/092.Reverse-Linked-List-II/092.Reverse-Linked-List-II_v2.cpp

@@ -0,0 +1,55 @@
+/**
+ * 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* reverseBetween(ListNode* head, int left, int right) 
+    {
+        ListNode* dummy = new ListNode(0);
+        dummy->next = head;
+
+        ListNode* p = dummy;
+        for (int i=0; i<right; i++)
+            p = p->next;
+        ListNode* c = p->next;
+        p->next = NULL;
+
+        p = dummy;
+        for (int i=0; i<left-1; i++)
+            p = p->next;
+        ListNode* b = p->next;
+        p->next = NULL;
+
+        b = reverseLinkedList(b);
+
+        p = dummy;
+        while (p->next) p = p->next;
+        p->next = b;
+        while (p->next) p = p->next;
+        p->next = c;
+
+        return dummy->next;
+    }
+
+    ListNode* reverseLinkedList(ListNode* h)
+    {
+        ListNode* last = NULL;
+        ListNode* cur = h;
+        ListNode* nxt;
+        while (cur)
+        {
+            nxt = cur->next;
+            cur->next = last;
+            last = cur;
+            cur = nxt;
+        }
+        return last;
+    }
+};