radix_sort.java

import java.util.Arrays;
import java.util.Scanner;

public class radix_sort {
 public static void main(String[] args) {
 // import scanner to take user input
 Scanner sc = new Scanner(System.in);
 System.out.println("enter the size of the array");
 int size = sc.nextInt();
 System.out.println("enter the element in the array");
 int[] arr = new int[size];
 // store the inputed elements in the array
 for(int i = 0; i<size; i++) {
 arr[i] = sc.nextInt();
 }
 // call our sorting function
 radixSort(arr);
 System.out.println(Arrays.toString(arr));
 }
 public static void radixSort(int[] arr) {
 // search for the maximum number to know the number of digits
 int max = getMax(arr);
 // do counting sort here
 for (int exp = 1; max/exp > 0; exp *= 10) {
 countingSort(arr, exp);
 }
 }
 
 public static void countingSort(int[] arr, int exp) { // sort the array by each digit starting with the least significant digit in the array
 int[] output = new int[arr.length]; // the final array in which we will store our answer
 int[] count = new int[10]; // the counting array

 // store all the counting occourences in count array
 for (int i = 0; i < arr.length; i++) {
 count[(arr[i]/exp)%10]++;
 }

 // change our element at count[i] to count[i-1] so that this contains actual position of the digit in output array
 for (int i = 1; i < 10; i++) {
 count[i] += count[i - 1];
 }

 // create our output array
 for (int i = arr.length - 1; i >= 0; i--) {
 output[count[(arr[i]/exp)%10] - 1] = arr[i];
 count[(arr[i]/exp)%10]--;
 }

 // store the output array in our ans array, so that numbers that are sorted now can be stored
 for (int i = 0; i < arr.length; i++) {
 arr[i] = output[i];
 }
 }

 // normal function to find the max value in our array
 public static int getMax(int[] arr) {
 int max = arr[0];
 for (int i = 1; i < arr.length; i++) {
 if (arr[i] > max) {
 max = arr[i];
 }
 }
 return max;
 }
}