Advent of Code 2017 - Day 6

Day6.java

package Advent2017;

import util.FileIO;

import java.util.*;
import java.util.stream.Collectors;

public class Day6 {

    private static int firstMax(List<Integer> a) {
        int max = Collections.max(a);
        return a.indexOf(max);
    }


    public static void main(String[] args) {

        List<Integer> nums = Arrays.stream(FileIO.getFileAsString("advent2017_day6.txt")
                            .split("\\s+"))
                .mapToInt(Integer::parseInt)
                .boxed()
                .collect(Collectors.toList());

        Map<List<Integer>, Integer> seen = new HashMap<>();

        seen.put(nums, 0);
        int steps = 0;

        while (true) {
            int index = firstMax(nums);
            int redistribute = nums.get(index);
            nums.set(index++, 0);
            while (redistribute-- > 0) {
                index %= nums.size();
                nums.set(index, nums.get(index++) + 1);
            }
            steps++;

            if (seen.containsKey(nums)) {
                System.out.println("Part 2: " + (steps - seen.get(nums)));
                break;
            }
            seen.put(nums, steps);


        }
        System.out.println("Part 1: " + steps);
    }
}