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3 | 3 | import com.sbaars.adventofcode.year15.Day2015; |
4 | 4 |
|
5 | 5 | public class Day25 extends Day2015 { |
| 6 | + private static final long FIRST_CODE = 20151125L; |
| 7 | + private static final long MULTIPLIER = 252533L; |
| 8 | + private static final long DIVISOR = 33554393L; |
| 9 | + |
6 | 10 | public Day25() { |
7 | 11 | super(25); |
8 | 12 | } |
9 | 13 |
|
10 | 14 | public static void main(String[] args) { |
11 | | - new Day25().printParts(); |
| 15 | + Day25 day = new Day25(); |
| 16 | + day.printParts(); |
| 17 | + new com.sbaars.adventofcode.network.Submit().submit(day.part1(), 2015, 25, 1); |
12 | 18 | } |
13 | 19 |
|
14 | 20 | @Override |
15 | 21 | public Object part1() { |
16 | | - return ""; |
| 22 | + String input = day().trim(); |
| 23 | + int targetRow = Integer.parseInt(input.replaceAll(".*row (\\d+).*", "1ドル")); |
| 24 | + int targetCol = Integer.parseInt(input.replaceAll(".*column (\\d+).*", "1ドル")); |
| 25 | + return findCode(targetRow, targetCol); |
17 | 26 | } |
18 | 27 |
|
19 | 28 | @Override |
20 | 29 | public Object part2() { |
21 | | - return ""; |
| 30 | + return "Merry Christmas!"; // There is no part 2 for Day 25 |
| 31 | + } |
| 32 | + |
| 33 | + private long findCode(int targetRow, int targetCol) { |
| 34 | + // Calculate the position in the sequence |
| 35 | + int position = getPositionInSequence(targetRow, targetCol); |
| 36 | + |
| 37 | + // Calculate the code at that position |
| 38 | + long code = FIRST_CODE; |
| 39 | + for (int i = 1; i < position; i++) { |
| 40 | + code = (code * MULTIPLIER) % DIVISOR; |
| 41 | + } |
| 42 | + return code; |
| 43 | + } |
| 44 | + |
| 45 | + private int getPositionInSequence(int row, int col) { |
| 46 | + // The position is the sum of all numbers in the diagonal before the target position |
| 47 | + // plus the position in the current diagonal |
| 48 | + int diagonalNum = row + col - 1; |
| 49 | + int positionsBeforeDiagonal = (diagonalNum * (diagonalNum - 1)) / 2; |
| 50 | + return positionsBeforeDiagonal + col; |
22 | 51 | } |
23 | 52 | } |
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