905: Sort Array By Parity

emanuelschmoczer · emanuelschmoczer · commit 36699aebd9d2 · 2025-06-03T00:04:09.000+02:00
diff --git a/README.md b/README.md
@@ -31,6 +31,7 @@ My solutions to LeetCode problems in Kotlin.
 |                       [773](https://leetcode.com/problems/sliding-puzzle/)                       |                                    [Sliding Puzzle](src/main/kotlin/com/schmoczer/leetcode/_0773/SlidingPuzzle.kt)                                    |    Hard    |
 |                       [796](https://leetcode.com/problems/rotate-string/)                        |                                     [Rotate String](src/main/kotlin/com/schmoczer/leetcode/_0796/RotateString.kt)                                     |    Easy    |
 |                 [876](https://leetcode.com/problems/middle-of-the-linked-list/)                  |                          [Middle of the Linked List](src/main/kotlin/com/schmoczer/leetcode/_0876/MiddleOfTheLinkedList.kt)                           |    Easy    |
+|                    [905](https://leetcode.com/problems/sort-array-by-parity/)                    |                               [Sort Array By Parity](src/main/kotlin/com/schmoczer/leetcode/_0905/SortArrayByParity.kt)                               |    Easy    |
 |                    [941](https://leetcode.com/problems/valid-mountain-array/)                    |                              [Valid Mountain Array](src/main/kotlin/com/schmoczer/leetcode/_0941/ValidMountainArray.kt)                               |    Easy    |
 |                 [977](https://leetcode.com/problems/squares-of-a-sorted-array/)                  |                          [Squares of a Sorted Array](src/main/kotlin/com/schmoczer/leetcode/_0977/SquaresOfASortedArray.kt)                           |    Easy    |
 |                      [1089](https://leetcode.com/problems/duplicate-zeros/)                      |                                   [Duplicate Zeros](src/main/kotlin/com/schmoczer/leetcode/_1089/DuplicateZeros.kt)                                   |    Easy    |
diff --git a/src/main/kotlin/com/schmoczer/leetcode/_0905/README.md b/src/main/kotlin/com/schmoczer/leetcode/_0905/README.md
@@ -0,0 +1,23 @@
+# Sort Array By Parity
+
+Given an integer array `nums`, move all the even integers at the beginning of the array followed by all the odd
+integers.
+
+Return any array that satisfies this condition.
+
+Example 1:
+
+> Input: nums = [3,1,2,4]
+>
+> Output: [2,4,3,1]
+
+Example 2:
+
+> Input: nums = [0]
+>
+> Output: [0]
+
+Constraints:
+
+- `1 <= nums.length <= 5000`
+- `0 <= nums[i] <= 5000`
diff --git a/src/main/kotlin/com/schmoczer/leetcode/_0905/SortArrayByParity.kt b/src/main/kotlin/com/schmoczer/leetcode/_0905/SortArrayByParity.kt
@@ -0,0 +1,17 @@
+package com.schmoczer.leetcode._0905
+
+class SortArrayByParity {
+    // Runtime 1ms Beats 96.34%
+    fun sortArrayByParity(nums: IntArray): IntArray {
+        var slow = 0
+        for (fast in 0 until nums.size) {
+            if (nums[fast] and 1 == 0) {
+                val number = nums[slow]
+                nums[slow] = nums[fast]
+                nums[fast] = number
+                slow++
+            }
+        }
+        return nums
+    }
+}
diff --git a/src/test/kotlin/com/schmoczer/leetcode/_0905/SortArrayByParityTest.kt b/src/test/kotlin/com/schmoczer/leetcode/_0905/SortArrayByParityTest.kt
@@ -0,0 +1,32 @@
+package com.schmoczer.leetcode._0905
+
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.params.ParameterizedTest
+import org.junit.jupiter.params.provider.Arguments
+import org.junit.jupiter.params.provider.MethodSource
+import kotlin.test.assertContentEquals
+
+class SortArrayByParityTest {
+    private companion object {
+        @JvmStatic
+        fun unsortedAndSorted() = listOf(
+            Arguments.of(intArrayOf(3, 1, 2, 4), intArrayOf(2, 4, 3, 1)),
+            Arguments.of(intArrayOf(0), intArrayOf(0)),
+        )
+    }
+
+    private lateinit var sut: SortArrayByParity
+
+    @BeforeEach
+    fun setUp() {
+        sut = SortArrayByParity()
+    }
+
+    @ParameterizedTest(name = "{0} sorted by parity is {1}")
+    @MethodSource("unsortedAndSorted")
+    fun `returns the array sorted by parity`(input: IntArray, expected: IntArray) {
+        val result = sut.sortArrayByParity(input)
+
+        assertContentEquals(expected, result)
+    }
+}
