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PigeonholeSort.java
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PigeonholeSort.java
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package com.thealgorithms.sorts;
import java.util.ArrayList;
public class PigeonholeSort {
/*
This code implements the pigeonhole sort algorithm for the integer array,
but we can also implement this for string arrays too.
See https://www.geeksforgeeks.org/pigeonhole-sort/
*/
void sort(Integer[] array) {
int maxElement = array[0];
for (int element : array) {
if (element > maxElement) maxElement = element;
}
int numOfPigeonholes = 1 + maxElement;
ArrayList<Integer>[] pigeonHole = new ArrayList[numOfPigeonholes];
for (int k = 0; k < numOfPigeonholes; k++) {
pigeonHole[k] = new ArrayList<>();
}
for (int t : array) {
pigeonHole[t].add(t);
}
int k = 0;
for (ArrayList<Integer> ph : pigeonHole) {
for (int elements : ph) {
array[k] = elements;
k = k + 1;
}
}
}
public static void main(String[] args) {
PigeonholeSort pigeonholeSort = new PigeonholeSort();
Integer[] arr = {8, 3, 2, 7, 4, 6, 8};
System.out.print("Unsorted order is : ");
SortUtils.print(arr);
pigeonholeSort.sort(arr);
System.out.print("Sorted order is : ");
for (int i = 0; i < arr.length; i++) {
assert (arr[i]) <= (arr[i + 1]);
}
SortUtils.print(arr);
}
}