Day8.java

package com.sbaars.adventofcode.year19.days;

import com.sbaars.adventofcode.common.ProcessesImages;
import com.sbaars.adventofcode.common.map.CountMap;
import com.sbaars.adventofcode.year19.Day2019;

import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;

public class Day8 extends Day2019 implements ProcessesImages {
  private static final int DIM_X = 6;
  private static final int DIM_Y = 25;
  private static final int SIZE = DIM_X * DIM_Y;

  public Day8() {
    super(8);
  }

  public static void main(String[] args) {
    new Day8().printParts();
  }

  @Override
  public Object part1() {
    int[] pixels = readPixels();
    var pixelCounts = countPixels(pixels);
    var cm = pixelCounts.stream().reduce((e1, e2) -> e1.get(0) > e2.get(0) ? e2 : e1).get();
    return cm.get(1) * cm.get(2);
  }

  private int[] readPixels() {
    char[] chars = day().toCharArray();
    return IntStream.range(0, chars.length).map(i -> Character.getNumericValue(chars[i])).toArray();
  }

  private List<CountMap<Integer>> countPixels(int[] pixels) {
    List<CountMap<Integer>> pixelCounts = new ArrayList<>();
    for (int i = 0; i < pixels.length; i += SIZE) {
      CountMap<Integer> cm = new CountMap<>();
      for (int j = i; j < i + SIZE; j++) {
        cm.increment(pixels[j]);
      }
      pixelCounts.add(cm);
    }
    return pixelCounts;
  }

  @Override
  public Object part2() {
    int[][] pixelArrays = splitArray(readPixels(), 100, SIZE);
    int[] finalPixels = determineFinalImage(pixelArrays);
    return printAsciiArray(splitArray(finalPixels, DIM_X, DIM_Y));
  }

  private int[] determineFinalImage(int[][] pixelArrays) {
    int[] finalPixels = pixelArrays[0];
    for (int i = 1; i < pixelArrays.length; i++)
      for (int j = 0; j < pixelArrays[i].length; j++)
        if (finalPixels[j] == 2)
          finalPixels[j] = pixelArrays[i][j];
    return finalPixels;
  }

  int[][] splitArray(int[] arr, int x, int y) {
    int[][] pixelArrays = new int[x][y];
    for (int i = 0; i < arr.length; i += y)
      for (int j = i; j < i + y; j++)
        pixelArrays[i / y][j - i] = arr[j];
    return pixelArrays;
  }
}