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