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RadixSort.java
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RadixSort.java
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/**
* RadixSort: sort an array of integers digit by digit sort starting from least
* significant digit to most significant digit. For every single digit, counting
* sort is considered.
*
* Time Complexity: O(wn) for n keys which are integers of word size w.
* Space Complexity: O(w + N).
*
*/
import java.util.Arrays;
public class RadixSort {
public static void sort(int[] arr) {
radixSort(arr, arr.length);
}
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);
}
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];
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];
}
public static void main(String[] args) {
int[] arr1 = {10, 3, 7, 5, 20, 15, 1};
MergeSort.sort(arr1);
System.out.println(Arrays.toString(arr1));
int[] arr2 = {};
MergeSort.sort(arr2);
System.out.println(Arrays.toString(arr2));
int[] arr3 = {10};
MergeSort.sort(arr3);
System.out.println(Arrays.toString(arr3));
}
}