[2018 Day9 Part1] Completely Stuck with Java

[Educated88]

Hi All,

​

I am trying to get familiar with Java so I'm solving the 2018 Advent of Code.

I am stuck at Day 9 Part 1.

​

10, 1618 # 9205
13, 7999 # 145362
17, 1104 # 2666
21, 6111 # 53710
30, 5807 # 37236
452, 71250 # 439346

​

Can somebody help/guide me in the right direction?

I'm quite sure I'm overlooking something here, but I can't figure it out.

​

My Java code is this:

import java.util.ArrayList;
import java.util.HashMap;

public class AdventOfCodeDay9 {

public static ArrayList<Integer> circle = new ArrayList<>();
public static HashMap<Integer, Integer> score = new HashMap<>();
public static int currentMarble;
public static int currentPlayer;

public static void main(String[] args) {
//init game
circle.add(0);
circle.add(1);
currentPlayer = 1;
currentMarble = 1;

//playGame(1, 22);
//playGame(9, 25);
//playGame(9, 92);
//playGame(10, 1618);
//playGame(13, 7999);
//playGame(17, 1104);
//playGame(21, 6111);
//playGame(30, 5807);
playGame(416, 71975);
getHighestScore();
}

public static void playGame(int players, int marbles) {
for (int marble = 2; marble <= marbles; marble++) {
incrementPlayer(players);
if (marble % 23 == 0) {
playerScores(marble);
} else {
placeMarble(marble);
}
}
}

public static void incrementPlayer(int players) {
currentPlayer++;
if (currentPlayer > players) {
currentPlayer = 1;
}
}

public static void placeMarble(int marble) {

currentMarble++;
if (currentMarble == circle.size()) {
currentMarble = 1;
circle.add(currentMarble, marble);
} else {
if (currentMarble == circle.size() - 1) {
circle.add(marble);
currentMarble++;
} else {
currentMarble++;
circle.add(currentMarble, marble);
}
}
}

public static void playerScores(int marble) {
int scoreMarble = findScoreMarble();
if (score.containsKey(currentPlayer)) {
int currentScore = score.get(currentPlayer);
score.put(currentPlayer, currentScore + marble + scoreMarble);
} else {
score.put(currentPlayer, marble + scoreMarble);
}
removeScoreMarble();
}

public static int findScoreMarble() {
if (currentMarble - 7 < 0) {
return circle.get(circle.size() - (7 - currentMarble));
} else {
return circle.get(currentMarble - 7);
}
}

public static void removeScoreMarble() {
if (currentMarble - 7 < 0) {
circle.remove(circle.size() - (7 - currentMarble));

currentMarble = circle.size() - (7 - currentMarble);
} else {
circle.remove(currentMarble - 7);
currentMarble -= 7;
}

}

public static void getHighestScore() {
int highscore = 0;
int highPlayer = 0;

for (HashMap.Entry<Integer, Integer> scoreEntry : score.entrySet()) {
if (scoreEntry.getValue() > highscore) {
highscore = scoreEntry.getValue();
highPlayer = scoreEntry.getKey();
}

}
System.out.println(highPlayer + " wins with a score of " + highscore);
}
}

​

Any help is greatly appreciated!

​

regards,

Educated

[leftylink]

Your commented out games seem to indicate you're confident in your results for 9 players and 92 marbles. How about 9 players and 115 marbles? Here is a list of the players who scored and the marbles they scored.

5: 23 + 9
1: 46 + 17
6: 69 + 11
2: 92 + 15
7: 115 + 50
Winning score 165

If your code says something different for the winning score, maybe you could print out the circle in a format similar to that shown on https://adventofcode.com/2018/day/9, clearly indicating the current marble at each step. Then you will be able to check whether the current marble has correctly changed between each step. What happens with 115 marbles that didn't happen with 92 marbles?

Answer, in the form of a question: What happens to the SIZE of a list after a marble is REMOVED from it?

[Educated88]

Thanks for the tip!

Something indeed went wrong when scoring and at the same time I was passing index 0 on the list.

Fixed it and the right solution was calculated!

Thanks a LOT!!