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import java.util.ArrayList;
import java.util.Map;
import java.util.TreeMap;
/**
*
* @author Youssef Ali (https://github.com/youssefAli11997)
*
*/
class CountingSort {
/**
* This method implements the Generic Counting Sort
*
* @param array The array to be sorted
* @param last The count of total number of elements in array
* Sorts the array in increasing order
* It uses array elements as keys in the frequency map
**/
public static <T extends Comparable<T>> void CS(T[] array, int last) {
Map<T, Integer> frequency = new TreeMap<T, Integer>();
// The final output array
ArrayList<T> sortedArray = new ArrayList<T>();
// Counting the frequency of @param array elements
for(T t : array) {
try{
frequency.put(t, frequency.get(t)+1);
}catch(Exception e){ // new entry
frequency.put(t, 1);
}
}
// Filling the sortedArray
for(Map.Entry<T, Integer> element : frequency.entrySet()) {
for(int j=0; j<element.getValue(); j++)
sortedArray.add(element.getKey());
}
for(int i=0; i<array.length; i++){
array[i] = sortedArray.get(i);
}
}
// Driver Program
public static void main(String[] args) {
// Integer Input
Integer[] arr1 = {4,23,6,78,1,54,231,9,12};
int last = arr1.length;
System.out.println("Before Sorting:");
for (int i=0;i<arr1.length;i++) {
System.out.print(arr1[i] + " ");
}
System.out.println();
CS(arr1, last);
// Output => 1 4 6 9 12 23 54 78 231
System.out.println("After Sorting:");
for (int i=0;i<arr1.length;i++) {
System.out.print(arr1[i] + " ");
}
System.out.println();
System.out.println("------------------------------");
// String Input
String[] array1 = {"c", "a", "e", "b","d"};
last = array1.length;
System.out.println("Before Sorting:");
for (int i=0;i<array1.length;i++) {
System.out.print(array1[i] + " ");
}
System.out.println();
CS(array1, last);
//Output => a b c d e
System.out.println("After Sorting:");
for(int i=0; i<last; i++) {
System.out.print(array1[i]+" ");
}
}
}