JavaAlgorithms/Sorts/RadixSort.java

package Sorts;

import java.util.Arrays;

class RadixSort {

  private static int getMax(int[] arr, int n) {
    int mx = arr[0];
    for (int i = 1; i < n; i++) if (arr[i] > mx) mx = arr[i];
    return mx;
  }

  private static void countSort(int[] arr, int n, int exp) {
    int[] output = new int[n];
    int i;
    int[] count = new int[10];
    Arrays.fill(count, 0);

    for (i = 0; i < n; i++) count[(arr[i] / exp) % 10]++;

    for (i = 1; i < 10; i++) count[i] += count[i - 1];

    for (i = n - 1; i >= 0; i--) {
      output[count[(arr[i] / exp) % 10] - 1] = arr[i];
      count[(arr[i] / exp) % 10]--;
    }

    for (i = 0; i < n; i++) arr[i] = output[i];
  }

  private static void radixsort(int[] arr, int n) {

    int m = getMax(arr, n);

    for (int exp = 1; m / exp > 0; exp *= 10) countSort(arr, n, exp);
  }

  static void print(int[] arr, int n) {
    for (int i = 0; i < n; i++) System.out.print(arr[i] + " ");
  }

  public static void main(String[] args) {
    int[] arr = {170, 45, 75, 90, 802, 24, 2, 66};
    int n = arr.length;
    radixsort(arr, n);
    print(arr, n);
  }
}
// Written by James Mc Dermott(theycallmemac)