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Implement in-place shuffle for arrays

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Minor: reorder shuffle/shuffled extensions more consistently

#KT-25651 Fixed
This commit is contained in:
Ilya Gorbunov
2020-03-26 21:52:11 +03:00
parent e58f1c8932
commit 15319eb88e
10 changed files with 487 additions and 43 deletions
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libraries/stdlib/test/collections/ArraysTest.kt
+59 -1
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@@ -1,5 +1,5 @@
/*
* Copyright 2010-2019 JetBrains s.r.o. and Kotlin Programming Language contributors.
* Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
* Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
*/
@@ -1856,6 +1856,64 @@ class ArraysTest {
array.iterator().assertSorted { a, b -> comparator.compare(a, b) <= 0 }
}
private inline fun <T> testShuffle(array: T, shuffle: T.() -> Unit, toList: T.() -> List<*>) {
val original = array.toList()
array.shuffle()
val shuffled = array.toList()
assertNotEquals(original, shuffled)
assertEquals(original.groupBy { it }, shuffled.groupBy { it })
}
@Test
fun shuffle() {
val numbers = List(100) { it }
testShuffle(numbers.map(Int::toInt).toIntArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toLong).toLongArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toByte).toByteArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toShort).toShortArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toFloat).toFloatArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toDouble).toDoubleArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toChar).toCharArray(), { shuffle() }, { toList() })
testShuffle(numbers.map { it % 2 == 0 }.toBooleanArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toUInt).toUIntArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toULong).toULongArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toUByte).toUByteArray(), { shuffle() }, { toList() })
testShuffle(numbers.map(Int::toUShort).toUShortArray(), { shuffle() }, { toList() })
testShuffle(arrayOf(1, "x", null, Any(), 'a', 2u, 5.0), { shuffle() }, { toList() })
}
private inline fun <T> testShuffleR(array: T, shuffle: T.(Random) -> Unit, toList: T.() -> List<*>) {
val seed = Random.nextInt()
val original = array.toList()
val originalShuffled = original.shuffled(Random(seed))
array.shuffle(Random(seed))
val shuffled = array.toList()
assertNotEquals(original, shuffled)
assertEquals(originalShuffled, shuffled)
}
@Test
fun shufflePredictably() {
val numbers = List(16) { it }
testShuffleR(numbers.map(Int::toInt).toIntArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toLong).toLongArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toByte).toByteArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toShort).toShortArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toFloat).toFloatArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toDouble).toDoubleArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toChar).toCharArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map { it % 2 == 0 }.toBooleanArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toUInt).toUIntArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toULong).toULongArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toUByte).toUByteArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(numbers.map(Int::toUShort).toUShortArray(), { r -> shuffle(r) }, { toList() })
testShuffleR(arrayOf(1, "x", null, Any(), 'a', 2u, 5.0), { r -> shuffle(r) }, { toList() })
}
@Test
fun elementAt() {
expect(0) { byteArrayOf(0, 1, 2).elementAt(0) }