7주차

Author: jdalma

reverse-linked-list/jdalma.kt

@@ -0,0 +1,36 @@
+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+
+class `reverse-linked-list` {
+
+    /**
+     * TC : O(n), SC: O(1)
+     */
+    fun reverseList(head: ListNode?): ListNode? {
+        var prev: ListNode? = null
+        var next: ListNode? = null
+        var curr: ListNode? = head
+
+        while (curr != null) {
+            next = curr.next
+            curr.next = prev
+            prev = curr
+            curr = next
+        }
+
+        return prev
+    }
+
+    @Test
+    fun `입력 받은 단일 리스트를 반전하고 반전한 목록을 반환한다`() {
+        reverseList(ListNode(1, ListNode(2, ListNode(3, ListNode(4, ListNode(5))))))
+            shouldBe(ListNode(5, ListNode(4, ListNode(3, ListNode(2, ListNode(1))))))
+    }
+}
+
+class ListNode(
+    var `val`: Int,
+    var next: ListNode? = null
+)