Data update

Task/Quickselect-algorithm/Kotlin/quickselect-algorithm.kts

@@ -0,0 +1,45 @@
+// version 1.1.2
+
+const val MAX = Int.MAX_VALUE
+val rand = java.util.Random()
+
+fun partition(list:IntArray, left: Int, right:Int, pivotIndex: Int): Int {
+    val pivotValue = list[pivotIndex]
+    list[pivotIndex] = list[right]
+    list[right] = pivotValue
+    var storeIndex = left
+    for (i in left until right) {
+        if (list[i] < pivotValue) {
+            val tmp = list[storeIndex]
+            list[storeIndex] = list[i]
+            list[i] = tmp
+            storeIndex++
+        }
+    }
+    val temp = list[right]
+    list[right] = list[storeIndex]
+    list[storeIndex] = temp
+    return storeIndex
+}
+
+tailrec fun quickSelect(list: IntArray, left: Int, right: Int, k: Int): Int {
+    if (left == right) return list[left]
+    var pivotIndex = left + Math.floor((rand.nextInt(MAX) % (right - left + 1)).toDouble()).toInt()
+    pivotIndex = partition(list, left, right, pivotIndex)
+    if (k == pivotIndex)
+        return list[k]
+    else if (k < pivotIndex)
+        return quickSelect(list, left, pivotIndex - 1, k)
+    else
+        return quickSelect(list, pivotIndex + 1, right, k)
+}
+
+fun main(args: Array<String>) {
+    val list = intArrayOf(9, 8, 7, 6, 5, 0, 1, 2, 3, 4)
+    val right = list.size - 1
+    for (k in 0..9) {
+        print(quickSelect(list, 0, right, k))
+        if (k < 9) print(", ")
+    }
+    println()
+}