implemented and tested radix sort

Author: Cory Thompson

sorting/radixsort/radixSort.test.ts

@@ -0,0 +1,37 @@
+import { radixSort } from "./radixSort";
+
+const fourDigitArray = [
+  1234,
+  5421,
+  3323,
+  4454,
+  1111,
+  2222,
+  3333,
+  5435,
+  4545,
+  2332,
+  3215
+];
+
+const fourDigitSortedArray = [
+  1111,
+  1234,
+  2222,
+  2332,
+  3215,
+  3323,
+  3333,
+  4454,
+  4545,
+  5421,
+  5435
+];
+
+test("radixSort", () => {
+  expect(radixSort([1, 2, 3, 4])).toEqual([1, 2, 3, 4]);
+  expect(radixSort([3, 2, 1, 4])).toEqual([1, 2, 3, 4]);
+  expect(radixSort([2, 3, 4, 1])).toEqual([1, 2, 3, 4]);
+  expect(radixSort([2, 3, 4, 1])).toEqual([1, 2, 3, 4]);
+  expect(radixSort(fourDigitArray)).toEqual(fourDigitSortedArray);
+});

sorting/radixsort/radixSort.ts

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+/**
+ * Radix Sort implemented in TypeScript
+ * https://github.com/AllAlgorithms/TypeScript
+ */
+
+function maxPlaceValue(arr: number[]): number {
+  let max = 0;
+  for (const num of arr) {
+    const digits = Math.floor(Math.log10(num) + 1);
+    max = Math.max(max, digits);
+  }
+
+  return max;
+}
+
+function getDigit(num: number, place: number): number {
+  return Math.floor(num / place) % 10;
+}
+
+export function radixSort(arr: number[]): number[] {
+  const digits = maxPlaceValue(arr);
+  let sortedArray = arr.slice();
+  for (let i = 1; i <= digits; i++) {
+    const place = Math.pow(10, i - 1); // ones place, tens place, etc
+
+    // create empty bucket of 10 empty arrays
+    const buckets: number[][] = [];
+    for (let i = 0; i < 10; i++) {
+      buckets.push([]);
+    }
+
+    for (const num of sortedArray) {
+      const digit = getDigit(num, place);
+      buckets[digit].push(num);
+    }
+
+    sortedArray = ([] as number[]).concat(...buckets);
+  }
+
+  return sortedArray;
+}