some-advent-of-code: 2247561a021d93ed526ef0036094c12d0ae9e8f2

     1: 
     2: import java.io.IOException;
     3: import java.nio.file.*;
     4: import java.util.*;
     5: 
     6: public class Exercise210702
     7: {
     8: 
     9: 	public static void main(
    10: 			String args[]
    11: 	) {
    12: 		final String here = "e210702.m ";
    13: 		if ( args.length < 1 )
    14: 		{
    15: 			throw new RuntimeException( here +"add a filename argument" );
    16: 		}
    17: 		String userSaysFile = args[ 0 ];
    18: 		List<String> fileLines = new LinkedList<>();
    19: 		try
    20: 		{
    21: 			Path where = Paths.get( userSaysFile );
    22: 			fileLines = Files.readAllLines( where );
    23: 		}
    24: 		catch ( IOException | InvalidPathException ie )
    25: 		{
    26: 			System.err.println( here +"couldn't read file "+ userSaysFile +" because "+ ie );
    27: 			return;
    28: 		}
    29: 		/*
    30: 		- interpretation of spec -
    31: 		for crab position
    32: 			increment number at that position
    33: 			update max
    34: 		for ( 1 - max position )
    35: 			for position
    36: 				increment cost * index
    37: 		*/
    38: 		Exercise210702.align( fileLines );
    39: 	}
    40: 
    41: 
    42: 	private static void align(
    43: 			List<String> fileLines
    44: 	) {
    45: 		String[] positionsStr = null;
    46: 		for ( String line : fileLines )
    47: 		{
    48: 			if ( line.isEmpty() )
    49: 				continue;
    50: 			positionsStr = line.split( "," );
    51: 		}
    52: 		boolean testing = true;
    53: 
    54: 		int maxPosition = 0;
    55: 		Map<Integer, Integer> position_crabs = new HashMap<>();
    56: 		for ( String position : positionsStr )
    57: 		{
    58: 			int crabPosition = Integer.parseInt( position );
    59: 			if ( position_crabs.containsKey( crabPosition ) )
    60: 				position_crabs.put( crabPosition, position_crabs.get( crabPosition ) +1 );
    61: 			else
    62: 				position_crabs.put( crabPosition, Integer.valueOf( 1 ) );
    63: 
    64: 			if ( crabPosition > maxPosition )
    65: 				maxPosition = crabPosition;
    66: 		}
    67: 		if ( testing )
    68: 		{
    69: 			for ( int ind = 0; ind <= maxPosition; ind++ )
    70: 			{
    71: 				if ( ind % 100 == 0 )
    72: 					System.out.println();
    73: 				if ( position_crabs.containsKey( ind )  )
    74: 					System.out.print( " "+ ind +"-"+ position_crabs.get( ind ) );
    75: 			}
    76: 			System.out.println();
    77: 		}
    78: 
    79: 		long minimumDistance = (long)Integer.MAX_VALUE;
    80: 		// ASK slow ?
    81: 		for ( int center = 0; center <= maxPosition; center++ )
    82: 		{
    83: 			long currentTotalDistance = 0;
    84: 			for ( int ind = 0; ind <= maxPosition; ind++ )
    85: 			{
    86: 				if ( position_crabs.containsKey( ind )  )
    87: 				{
    88: 					int crabsHere = position_crabs.get( ind );
    89: 					currentTotalDistance += crabsHere * fuelCost( Math.abs( center - ind ) );
    90: 					if ( currentTotalDistance > minimumDistance )
    91: 						break; // ASK part 2 ?
    92: 				}
    93: 			}
    94: 			if ( currentTotalDistance < minimumDistance )
    95: 			{
    96: 				minimumDistance = currentTotalDistance;
    97: 				if ( testing )
    98: 					System.out.println( "cmin at "+ center +" is "+ minimumDistance );
    99: 			}
   100: 		}
   101: 
   102: 		System.out.println( "\t"+ minimumDistance );
   103: 	}
   104: 
   105: 
   106: 	private static int fuelCost(
   107: 			int distance
   108: 	) {
   109: 		int total = 0;
   110: 		for ( int step = 1; step <= distance; step++ )
   111: 			total += step;
   112: 		return total;
   113: 	}
   114: 
   115: 
   116: }
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