September 2017 Update

Task/Sorting-algorithms-Radix-sort/Kotlin/sorting-algorithms-radix-sort.kotlin

@@ -0,0 +1,36 @@
+// version 1.1.2
+
+fun radixSort(original: IntArray): IntArray {
+    var old = original // Need this to be mutable
+    // Loop for every bit in the integers
+    for (shift in 31 downTo 0) {
+        val tmp = IntArray(old.size)  // The array to put the partially sorted array into
+        var j = 0                     // The number of 0s
+        // Move the 0s to the new array, and the 1s to the old one
+        for (i in 0 until old.size) {
+            // If there is a 1 in the bit we are testing, the number will be negative
+            val move = (old[i] shl shift) >= 0
+            // If this is the last bit, negative numbers are actually lower
+            val toBeMoved = if (shift == 0) !move else move
+            if (toBeMoved)
+                tmp[j++] = old[i]
+            else {
+                // It's a 1, so stick it in the old array for now
+                old[i - j] = old[i]
+            }
+        }
+        // Copy over the 1s from the old array
+        for (i in j until tmp.size) tmp[i] = old[i - j]
+        // And now the tmp array gets switched for another round of sorting
+        old = tmp
+    }
+    return old
+}
+
+fun main(args: Array<String>) {
+    val arrays = arrayOf(
+        intArrayOf(170, 45, 75, -90, -802, 24, 2, 66),
+        intArrayOf(-4, 5, -26, 58, -990, 331, 331, 990, -1837, 2028)
+    )
+    for (array in arrays) println(radixSort(array).contentToString())
+}