문제 추가

Author: jdalma

house-robber/jdalma.kt

@@ -0,0 +1,65 @@
+package leetcode_study
+
+import io.kotest.matchers.shouldBe
+import org.junit.jupiter.api.Test
+import kotlin.math.max
+
+class `house-robber` {
+
+    fun rob(nums: IntArray): Int {
+        return usingDP(nums)
+    }
+
+    /**
+     * TC: O(n), SC: O(n)
+     */
+    private fun usingDP(nums: IntArray): Int {
+        val dp = IntArray(nums.size + 1).apply {
+            this[0] = 0
+            this[1] = nums[0]
+        }
+        for (index in 1 until nums.size) {
+            dp[index + 1] = max(nums[index] + dp[index - 1], dp[index])
+        }
+
+        return dp[nums.size]
+    }
+
+    /**
+     * TC: O(n), SC: O(n)
+     */
+    private fun usingMemoization(nums: IntArray): Int {
+        val memo = IntArray(nums.size) { -1 }
+        fun recursive(index: Int): Int {
+            return if (index > nums.size - 1) 0
+            else if (memo[index] != -1) memo[index]
+            else {
+                memo[index] = max(nums[index] + recursive(index + 2), recursive(index + 1))
+                memo[index]
+            }
+        }
+
+        return recursive(0)
+    }
+
+    /**
+     * 시간초과
+     * TC: O(2^n), SC: O(n)
+     */
+    private fun usingRecursive(nums:IntArray): Int {
+        fun recursive(index: Int, depth: Int): Int {
+            if (index > nums.size - 1) return 0
+            println("${"-".repeat(depth)} : max($index + ${index + 2}, ${index + 1})")
+            return max(nums[index] + recursive(index + 2, depth + 1), recursive(index + 1, depth + 1))
+        }
+
+        return recursive(0, 0)
+    }
+
+    @Test
+    fun `인접하지 않은 원소를 선택하여 최대의 합을 반환한다`() {
+        rob(intArrayOf(1,2,3,1)) shouldBe 4
+        rob(intArrayOf(2,7,9,3,1)) shouldBe 12
+        rob(intArrayOf(8,7,9,11,1)) shouldBe 19
+    }
+}