60 lines
1.5 KiB
Java
60 lines
1.5 KiB
Java
package Maths;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.Collections;
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import java.util.HashMap;
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/*
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* Find the mode of an array of numbers
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*
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* The mode of an array of numbers is the most frequently occurring number in the array,
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* or the most frequently occurring numbers if there are multiple numbers with the same frequency
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*/
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public class Mode {
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public static void main(String[] args) {
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/* Test array of integers */
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assert (mode(new int[] {})) == null;
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assert Arrays.equals(mode(new int[] {5}), new int[] {5});
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assert Arrays.equals(mode(new int[] {1, 2, 3, 4, 5}), new int[] {1, 2, 3, 4, 5});
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assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 8}), new int[] {7});
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assert Arrays.equals(mode(new int[] {7, 9, 9, 4, 5, 6, 7, 7, 9}), new int[] {7, 9});
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}
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/*
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* Find the mode of an array of integers
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*
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* @param numbers array of integers
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* @return mode of the array
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*/
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public static int[] mode(int[] numbers) {
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if (numbers.length == 0) return null;
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HashMap<Integer, Integer> count = new HashMap<>();
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for (int num : numbers) {
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if (count.containsKey(num)) {
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count.put(num, count.get(num) + 1);
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} else {
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count.put(num, 1);
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}
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}
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int max = Collections.max(count.values());
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ArrayList<Integer> modes = new ArrayList<>();
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for (int num : count.keySet()) {
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if (count.get(num) == max) {
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modes.add(num);
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}
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}
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return modes.stream().mapToInt(n -> n).toArray();
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}
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}
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