[정현준] 9주차

find-minimum-in-rotated-sorted-array/jdalma.kt

@@ -0,0 +1,34 @@
+class `find-minimum-in-rotated-sorted-array` {
+
+    /**
+     * TC: O(log N), SC: O(1)
+     */
+    fun findMin(nums: IntArray): Int {
+        var (low, high) = 0 to nums.size - 1
+
+        while (low + 1 < high) {
+            val mid = (low + high) / 2
+            if (nums[mid - 1] > nums[mid]) {
+                return nums[mid]
+            }
+            if (nums[mid] < nums[high]) {
+                high = mid
+            }
+            else {
+                low = mid
+            }
+        }
+
+        return min(nums[low], nums[high])
+    }
+
+    @Test
+    fun `입력받은 정수 배열의 최소 원소를 반환한다`() {
+        findMin(intArrayOf(4,5,6,7,0,1,2)) shouldBe 0
+        findMin(intArrayOf(2,3,0,1)) shouldBe 0
+        findMin(intArrayOf(2,3,1)) shouldBe 1
+        findMin(intArrayOf(2,1,3)) shouldBe 1
+        findMin(intArrayOf(2,3,4,5,1)) shouldBe 1
+        findMin(intArrayOf(11,13,15,17)) shouldBe 11
+    }
+}

linked-list-cycle/jdalma.kt

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+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+
+class `linked-list-cycle` {
+
+    data class ListNode(var `val`: Int) {
+        var next: ListNode? = null
+    }
+
+    /**
+     * TC: O(n), SC: O(1)
+     */
+    fun hasCycle(head: ListNode?): Boolean {
+        if (head == null) return false
+
+        var slow = head
+        var fast = head
+
+        while (fast?.next != null) {
+            slow = slow?.next
+            fast = fast.next?.next
+
+            if (slow == fast) return true
+        }
+
+        return false
+    }
+
+    @Test
+    fun `입력받은 노드에 사이클이 존재한다면 참을 반환한다`() {
+        val three = ListNode(3)
+        val two = ListNode(2)
+        val zero = ListNode(0)
+        val four = ListNode(4)
+
+        three.next = two
+        two.next = zero
+        zero.next = four
+        four.next = two
+
+        hasCycle(three) shouldBe true
+    }
+}