DeleteOccurrencesOfAnElement.java

package me.m_zebrak.kyu6;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Alice and Bob were on a holiday. Both of them took many pictures of the places they've been, and now they want to
 * show Charlie their entire collection. However, Charlie doesn't like these sessions, since the motive usually
 * repeats. He isn't fond of seeing the Eiffel tower 40 times. He tells them that he will only sit during the session
 * if they show the same motive at most N times. Luckily, Alice and Bob are able to encode the motive as a number.
 * Can you help them to remove numbers such that their list contains each number only up to N times, without changing
 * the order?
 * <p>
 * Task
 * Given a list lst and a number N, create a new list that contains each number of lst at most N times without
 * reordering. For example if N = 2, and the input is [1,2,3,1,2,1,2,3], you take [1,2,3,1,2], drop the next [1,2]
 * since this would lead to 1 and 2 being in the result 3 times, and then take 3, which leads to [1,2,3,1,2,3].
 * <p>
 * Example
 * EnoughIsEnough.deleteNth(new int[] {20,37,20,21}, 1) // return [20,37,21]
 * EnoughIsEnough.deleteNth(new int[] {1,1,3,3,7,2,2,2,2}, 3) // return [1, 1, 3, 3, 7, 2, 2, 2]
 */
public class DeleteOccurrencesOfAnElement  /*if it occurs more than n times*/ {
    public static int[] solution(int[] elements, int n) {
        List<Integer> lst = new ArrayList();

        for (Integer e : elements)
            if (Collections.frequency(lst, e) < n) lst.add(e);

        return lst.stream().mapToInt(i -> i).toArray();
    }
}