Solve 'Best travel' kata

borisskert · May 10, 2024 · facd21d · facd21d
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diff --git a/src/main/kotlin/besttravel/chooseBestSum.kt b/src/main/kotlin/besttravel/chooseBestSum.kt
@@ -0,0 +1,42 @@
+package besttravel
+
+/**
+ * https://www.codewars.com/kata/55e7280b40e1c4a06d0000aa/train/kotlin
+ */
+fun chooseBestSum(t: Int, k: Int, ls: List<Int>): Int {
+    return ls.combinations(k)
+        .map { it.sum() }
+        .filter { it <= t }
+        .maxOrNull() ?: -1
+}
+
+fun <T> List<T>.combinations(k: Int, acc: List<T> = emptyList()): List<List<T>> {
+    if (k == 0) return listOf(acc)
+    if (isEmpty()) return emptyList()
+
+    return drop(1)
+        .combinations(k - 1, acc + first()) + drop(1).combinations(k, acc)
+}
+
+// best practice (a lot of faster)
+
+//fun chooseBestSum(t: Int, k: Int, ls: List<Int>): Int {
+//    return ls.findBestCombination(k, { it.sum() }, t)?.sum() ?: -1
+//}
+//
+//fun <T, R : Comparable<R>> List<T>.findBestCombination(
+//    k: Int,
+//    f: (List<T>) -> R?,
+//    max: R,
+//    found: List<T> = emptyList(),
+//    n: Int = 0
+//): (List<T>)? {
+//    val result = f(found)
+//    if (k == 0 && (result == null || result <= max)) return found
+//    if (result != null && result > max || n >= size) return null
+//
+//    val a = findBestCombination(k - 1, f, max, found + get(n), n + 1)
+//    val b = findBestCombination(k, f, max, found, n + 1)
+//
+//    return if (a == null) b else if (b == null) a else if (f(a)!! > f(b)!!) a else b
+//}
diff --git a/src/test/kotlin/besttravel/ChooseBestSumKtTest.kt b/src/test/kotlin/besttravel/ChooseBestSumKtTest.kt
@@ -0,0 +1,91 @@
+package besttravel
+
+import org.junit.Assert.assertEquals
+import org.junit.Ignore
+import org.junit.Test
+
+class SumOfKTest {
+
+    @Test
+    fun basicTests1() {
+        println("****** Basic Tests small numbers******")
+        var ts = listOf(50, 55, 56, 57, 58)
+        val n = chooseBestSum(163, 3, ts)
+        assertEquals(163, n.toLong())
+        ts = listOf(50)
+        val m = chooseBestSum(163, 3, ts)
+        assertEquals(-1, m)
+    }
+
+    @Test
+    @Ignore("Performance test (~ 4 seconds on M3 Pro)")
+    fun hardPerformanceTest() {
+        val ts: List<Int> = listOf(
+            931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897, 455, 242, 564, 873, 586, 336,
+            934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636, 428, 943, 653, 862, 929, 645,
+            251, 665, 120, 750, 420, 340, 931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897,
+            455, 242, 564, 873, 586, 336, 934, 208, 557, 876, 644
+        )
+
+        val start = System.currentTimeMillis()
+        val n: Int = chooseBestSum(3198, 5, ts)
+        val end = System.currentTimeMillis()
+        println("Time: " + (end - start) + " ms")
+        assertEquals(3198, n.toLong())
+    }
+
+    @Test
+    @Ignore("Performance test (~ 10 seconds on M3 Pro)")
+    fun harderPerformanceTest() {
+        val ts: List<Int> = listOf(
+            931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897, 455, 242, 564, 873, 586, 336,
+            934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636, 428, 943, 653, 862, 929, 645,
+            251, 665, 120, 750, 420, 340, 931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897,
+            455, 242, 564, 873, 586, 336, 934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636
+        )
+
+        val start = System.currentTimeMillis()
+        val n: Int = chooseBestSum(3198, 5, ts)
+        val end = System.currentTimeMillis()
+        println("Time: " + (end - start) + " ms")
+        assertEquals(3198, n.toLong())
+    }
+
+    @Test
+    @Ignore("Performance test (~ 20 seconds on M3 Pro)")
+    fun evenHarderPerformanceTest() {
+        val ts: List<Int> = listOf(
+            931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897, 455, 242, 564, 873, 586, 336,
+            934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636, 428, 943, 653, 862, 929, 645,
+            251, 665, 120, 750, 420, 340, 931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897,
+            455, 242, 564, 873, 586, 336, 934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636,
+            428, 943, 653, 862, 929, 645, 251, 665, 120, 750
+        )
+
+        val start = System.currentTimeMillis()
+        val n: Int = chooseBestSum(3198, 5, ts)
+        val end = System.currentTimeMillis()
+        println("Time: " + (end - start) + " ms")
+        assertEquals(3198, n.toLong())
+    }
+
+    @Test
+    @Ignore("Performance test")
+    fun evenHardestPerformanceTest() {
+        val ts: List<Int> = listOf(
+            931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897, 455, 242, 564, 873, 586, 336,
+            934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636, 428, 943, 653, 862, 929, 645,
+            251, 665, 120, 750, 420, 340, 931, 744, 763, 825, 713, 851, 867, 435, 726, 112, 847, 697, 547, 384, 897,
+            455, 242, 564, 873, 586, 336, 934, 208, 557, 876, 644, 934, 753, 664, 725, 941, 754, 563, 972, 683, 636,
+            428, 943, 653, 862, 929, 645, 251, 665, 120, 750, 420, 340, 931, 744, 763, 825, 713, 851, 867, 435, 726,
+            112, 847, 697, 547, 384, 897, 455, 242, 564, 873, 586, 336, 934, 208, 557, 876, 644, 934, 753, 664, 725,
+            941, 754, 563, 972, 683, 636, 428, 943, 653, 862, 929, 645, 251, 665, 120, 750, 420, 340, 931, 744, 763,
+        )
+
+        val start = System.currentTimeMillis()
+        val n: Int = chooseBestSum(3198, 5, ts)
+        val end = System.currentTimeMillis()
+        println("Time: " + (end - start) + " ms")
+        assertEquals(3198, n.toLong())
+    }
+}