Filter Even Numbers (Loop vs Streams)

Problem

Print the even numbers of the array in the same order. Print nothing (an empty line) if there are none.

Constraints

  • 1 <= n <= 10^5

Examples

Input

6
1 2 3 4 5 6

Output

2 4 6

Solutions

AlternativeTime O(n)Space O(n)

Without streams you need a loop and a temporary list. The loop is clear and works in every Java version.

Same code works in Java810172125Basic features only, so nothing changes between versions.
/*
 * Problem : Process an array.
 * Input   : n, then n integers.
 * Output  : The even numbers.
 * Approach: Filter the array.
 * Time    : O(n)
 * Space   : O(n)
 * Java    : 8 or newer.
 */
import java.util.Scanner;
import java.util.Arrays;
import java.util.stream.Collectors;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static int[] solve(int[] a) {
        // Step 1: Before Java 16 we used a loop and a list to keep the even numbers.
        java.util.List<Integer> evens = new java.util.ArrayList<>();
        for (int value : a) {
            if (value % 2 == 0) {
                evens.add(value);
            }
        }

        // Step 2: Copy the list into an int array.
        int[] result = new int[evens.size()];
        for (int i = 0; i < result.length; i++) {
            result[i] = evens.get(i);
        }
        return result;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int size = scanner.nextInt();
        int[] a = new int[size];
        for (int i = 0; i < size; i++) {
            a[i] = scanner.nextInt();
        }
        System.out.println(Arrays.stream(solve(a)).mapToObj(String::valueOf).collect(Collectors.joining(" ")));
    }
}
Hints (1)
  1. Which numbers have value % 2 == 0?