add radix sort

Author: kimbo

sorting-algorithms.js

@@ -182,8 +182,46 @@ function combSort(arr) {
  return arr;
 }
 
-// TEST CASES
+function radixSort(arr) {
+
+ function numDigits(n, base=10) {
+ let i;
+ for (i = 1; base**(i-1) < n; i++) {}
+ return Math.max(Math.floor(i-1), 1);
+ }
+
+ function getDigit(num, i) {
+ return Math.floor(num / (10**(i-1))) % 10;
+ }
+
+ let maxNumDigits = 0;
+ for (let i = 0; i < arr.length; i++) {
+ let nDigits = numDigits(arr[i]);
+ if (nDigits > maxNumDigits) {
+ maxNumDigits = nDigits;
+ }
+ }
+
+ for (let digitPos = 1; digitPos <= maxNumDigits; digitPos++) {
+ let buckets = [[],[],[],[],[],[],[],[],[],[]];
+ for (let i = 0; i < arr.length; i++) {
+ let digit = getDigit(arr[i], digitPos);
+ if (isNaN(digit)) {
+ continue
+ }
+ buckets[digit].push(arr[i]);
+ }
+ for (let i = 0, k = 0; i < buckets.length; i++) {
+ for (let j = 0; j < buckets[i].length; j++) {
+ arr[k++] = buckets[i][j];
+ }
+ }
+ }
 
+ return arr;
+}
+
+// TEST CASES
 
 function runTests() {
 
@@ -208,6 +246,7 @@ function runTests() {
  bubbleSort,
  shellSort,
  combSort,
+ radixSort,
  ];
 
  sortFunctions.forEach(function(sort) {