Create 206.Reverse-Linked-List_Recursion.cpp

Bonnie404 · Nov 22, 2021 · fe801dc · fe801dc
1 parent a618066
commit fe801dc
Showing 1 changed file with 25 additions and 0 deletions.
diff --git a/Linked_List/206.Reverse-Linked-List/206.Reverse-Linked-List_Recursion.cpp b/Linked_List/206.Reverse-Linked-List/206.Reverse-Linked-List_Recursion.cpp
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+/**
+ * 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* reverseList(ListNode* head) 
+    {
+        return helper(NULL, head);
+    }
+
+    ListNode* helper(ListNode*last, ListNode* head)
+    {
+        if (head==NULL) return last;
+        ListNode* nxt = head->next;
+        head->next = last;
+        return helper(head, nxt);
+    }
+};