#247 Reorder List

Author: forest000014

reorder-list/forest000014.java

@@ -0,0 +1,49 @@
+/*
+# Time Complexity: O(n)
+# Space Complexity: O(1)
+# Solution
+Dale 님의 솔루션을 참고했습니다.
+*/
+
+/**
+ * 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 {
+    public void reorderList(ListNode head) {
+        ListNode slow = head;
+        ListNode fast = head;
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+        }
+
+        ListNode curr = slow.next;
+        slow.next = null;
+
+        ListNode prev = null;
+        while (curr != null) {
+            ListNode tempNext = curr.next;
+            curr.next = prev;
+            prev = curr;
+            curr = tempNext;
+        }
+
+        ListNode left = head;
+        ListNode right = prev;
+        while (right != null) {
+            ListNode leftNext = left.next;
+            ListNode rightNext = right.next;
+            left.next = right;
+            right.next = leftNext;
+            left = leftNext;
+            right = rightNext;
+        }
+    }
+}