Java/Maths/Mode.java at master · loisoft/Java · GitHub

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package Maths;

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

import java.util.HashMap;

* Find the mode of an array of numbers

* The mode of an array of numbers is the most frequently occurring number in the array,

* or the most frequently occurring numbers if there are multiple numbers with the same frequency

public class Mode {

public static void main(String[] args) {

/* Test array of integers */

assert (mode(new int[] {})) == null;

assert Arrays.equals(mode(new int[] {5}), new int[] {5});

assert Arrays.equals(mode(new int[] {1, 2, 3, 4, 5}), new int[] {1, 2, 3, 4, 5});

assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 8}), new int[] {7});

assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 9}), new int[] {7, 9});

}

* Find the mode of an array of integers

* @param numbers array of integers

* @return mode of the array

public static int[] mode(int[] numbers) {

if (numbers.length == 0) return null;

HashMap<Integer, Integer> count = new HashMap<>();

for (int num : numbers) {

if (count.containsKey(num)) {

count.put(num, count.get(num) + 1);

} else {

count.put(num, 1);

}

int max = Collections.max(count.values());

ArrayList<Integer> modes = new ArrayList<>();

for (int num : count.keySet()) {

if (count.get(num) == max) {

modes.add(num);

}

return modes.stream().mapToInt(n -> n).toArray();

}

Java/Maths/Mode.java at master · loisoft/Java · GitHub

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