Add Radix Sort test

Author: LyangHiga

src/sort/radixSort.test.ts

@@ -0,0 +1,16 @@
+import radixSort from "./radixSort";
+
+describe("Radix Sort Test", () => {
+  test("Testing if RS sort a random array", () => {
+    const nTimes = 100;
+    const SIZE = 100;
+    for (let i = 0; i < nTimes; i++) {
+      const arr = Array.from({ length: SIZE }, () =>
+        Math.floor(Math.random() * 1000)
+      );
+      const sortedArr = radixSort(arr);
+      const jsSortedArr = arr.slice().sort((a, b) => a - b);
+      expect(sortedArr).toEqual(jsSortedArr);
+    }
+  });
+});

src/sort/radixSort.ts

@@ -7,34 +7,35 @@ const getDigit = (num: number, place: number) => {
 const digitCount = (num: number) => {
   // log 0
   if (num === 0) return 1;
-  return Math.floor(Math.log10(num)) + 1;
+  return Math.floor(Math.log10(Math.abs(num))) + 1;
 };
 
-// returns the number of digits in the largest number of the list nums
-const mostDigits = (nums: number[]) => {
+// returns the number of digits in the largest number of the list arr
+const maximumDigits = (arr: number[]) => {
   let max = 0;
-  for (let i = 0; i < nums.length; i++) {
-    max = Math.max(max, nums[i]);
+  for (let n of arr) {
+    max = Math.max(max, digitCount(n));
   }
+
   return max;
 };
 
-const radixSort = (nums: number[]) => {
-  let maxDigits = mostDigits(nums);
+const radixSort = (arr: number[]) => {
+  let maxDigits = maximumDigits(arr);
   // put each digit from each num in the right bucket
   for (let i = 0; i < maxDigits; i++) {
     // an array of 10 empty arrays, a bucket to each possible number
     let digitBuckets: number[][] = Array.from({ length: 10 }, () => []);
-    for (let j = 0; j < nums.length; j++) {
-      // take the digit of nums[j]
-      let digit = getDigit(nums[j], i);
-      // add this nums[j] in the bucket of the right digit
-      digitBuckets[digit].push(nums[j]);
+    for (let j = 0; j < arr.length; j++) {
+      // take the digit of arr[j]
+      let digit = getDigit(arr[j], i);
+      // add this arr[j] in the bucket of the right digit
+      digitBuckets[digit].push(arr[j]);
     }
     // to concate each element from each bucket, using spread
-    nums = Array.prototype.concat(...digitBuckets);
+    arr = Array.prototype.concat(...digitBuckets);
   }
-  return nums;
+  return arr;
 };
 
-export = radixSort;
+export default radixSort;