reverse-linked-list solution

Author: chjung99

reverse-linked-list/chjung99.java

@@ -0,0 +1,39 @@
+/**
+ * time: O(n)
+ * space: O(1)
+ */
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode() {}
+ *     ListNode(int val) { this.val = val; }
+ *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    ListNode tail;
+    public ListNode reverseList(ListNode head) {
+        reverseNode(head);
+        return tail;
+    }
+
+    public void reverseNode(ListNode node){
+        if (node == null) return;
+        if (node.next == null) {
+            tail = node;
+            return;
+        }
+
+        ListNode nextNode = node.next;
+        node.next = null;
+
+        reverseNode(nextNode);
+
+        nextNode.next = node;
+
+    }
+}
+