> T[] sort(T[] unsorted) {
return sort(Arrays.asList(unsorted)).toArray(unsorted);
}
/**
* This method implements the Generic Counting Sort
*
* @param list The list to be sorted
*
* Sorts the list in increasing order
* The method uses list elements as keys in the frequency map
**/
@Override
public > List sort(List list) {
Map frequency = new TreeMap<>();
// The final output array
List sortedArray = new ArrayList<>(list.size());
// Counting the frequency of @param array elements
list.forEach(v -> frequency.put(v, frequency.getOrDefault(v, 0) + 1));
// Filling the sortedArray
for (Map.Entry element : frequency.entrySet()) {
for (int j = 0; j < element.getValue(); j++) {
sortedArray.add(element.getKey());
}
}
return sortedArray;
}
/**
* Stream Counting Sort
* The same as method {@link CountingSort#sort(List)} } but this method uses stream API
*
* @param list The list to be sorted
**/
private static > List streamSort(List list) {
return list.stream()
.collect(toMap(k -> k, v -> 1, (v1, v2) -> v1 + v2, TreeMap::new))
.entrySet()
.stream()
.flatMap(entry -> IntStream.rangeClosed(1, entry.getValue()).mapToObj(t -> entry.getKey()))
.collect(toList());
}
// Driver Program
public static void main(String[] args) {
// Integer Input
List unsortedInts = Stream.of(4, 23, 6, 78, 1, 54, 23, 1, 9, 231, 9, 12).collect(toList());
CountingSort countingSort = new CountingSort();
System.out.println("Before Sorting:");
print(unsortedInts);
// Output => 1 1 4 6 9 9 12 23 23 54 78 231
System.out.println("After Sorting:");
print(countingSort.sort(unsortedInts));
System.out.println("After Sorting By Streams:");
print(streamSort(unsortedInts));
System.out.println("\n------------------------------\n");
// String Input
List unsortedStrings = Stream.of("c", "a", "e", "b", "d", "a", "f", "g", "c").collect(toList());
System.out.println("Before Sorting:");
print(unsortedStrings);
//Output => a a b c c d e f g
System.out.println("After Sorting:");
print(countingSort.sort(unsortedStrings));
System.out.println("After Sorting By Streams:");
print(streamSort(unsortedStrings));
}
}