RadixSort.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 curent 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); 
	} 
}