Java Program for Radix Sort

Last Updated : 16 Aug, 2022

The Radix Sort Algorithm

Do the following for each digit i where i varies from the least significant digit to the most significant digit.
- Sort input array using counting sort (or any stable sort) according to the ith digit.

java

// Radix sort Java implementation 
import java.io.*; 
import java.util.*; 
 
class Radix { 
 
    // A utility function to get maximum value in arr[] 
    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; 
    } 
 
    // A function to do counting sort of arr[] according to 
    // the digit represented by exp. 
    static void countSort(int arr[], int n, int exp) 
    { 
        int output[] = new int[n]; // output array 
        int i; 
        int count[] = new int[10]; 
        Arrays.fill(count,0); 
 
        // Store count of occurrences in count[] 
        for (i = 0; i < n; i++) 
            count[ (arr[i]/exp)%10 ]++; 
 
        // Change count[i] so that count[i] now contains 
        // actual position of this digit in output[] 
        for (i = 1; i < 10; i++) 
            count[i] += count[i - 1]; 
 
        // Build the output array 
        for (i = n - 1; i >= 0; i--) 
        { 
            output[count[ (arr[i]/exp)%10 ] - 1] = arr[i]; 
            count[ (arr[i]/exp)%10 ]--; 
        } 
 
        // Copy the output array to arr[], so that arr[] now 
        // contains sorted numbers according to current digit 
        for (i = 0; i < n; i++) 
            arr[i] = output[i]; 
    } 
 
    // The main function to that sorts arr[] of size n using 
    // Radix Sort 
    static void radixsort(int arr[], int n) 
    { 
        // Find the maximum number to know number of digits 
        int m = getMax(arr, n); 
 
        // Do counting sort for every digit. Note that instead 
        // of passing digit number, exp is passed. exp is 10^i 
        // where i is current digit number 
        for (int exp = 1; m/exp > 0; exp *= 10) 
            countSort(arr, n, exp); 
    } 
 
    // A utility function to print an array 
    static void print(int arr[], int n) 
    { 
        for (int i=0; i<n; i++) 
            System.out.print(arr[i]+" "); 
    } 
 
 
    /*Driver function to check for above function*/
    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); 
    } 
} 
/* This code is contributed by Devesh Agrawal */