some-advent-of-code: 9d5afa0c7045e2d9faec180fe3a59e74480b509a

     1: 
     2: import java.io.IOException;
     3: import java.nio.file.*;
     4: import java.util.*;
     5: 
     6: public class Exercise210602
     7: {
     8: 
     9: 	public static void main(
    10: 			String args[]
    11: 	) {
    12: 		final String here = "e210602.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: 		*/
    32: 		Exercise210602.simulateFish( fileLines );
    33: 	}
    34: 
    35: 
    36: 	private static void simulateFish(
    37: 			List<String> fileLines
    38: 	) {
    39: 		boolean testing = true;
    40: 		final int bornGenInd = 8, postBirthGenInd = 6;
    41: 		long[] generations = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
    42: 		for ( String line : fileLines )
    43: 		{
    44: 			if ( line.isEmpty() )
    45: 				continue;
    46: 			String[] initialPopulation = line.split( "," );
    47: 			for ( int ind = 0; ind < initialPopulation.length; ind++ )
    48: 			{
    49: 				int oneFishAge = Integer.parseInt( initialPopulation[ ind ] );
    50: 				generations[ oneFishAge ] += 1L;
    51: 			}
    52: 		}
    53: 
    54: 		for ( int days = 256; days > 0; days-- )
    55: 		{
    56: 			long temp, tempForGenZero;
    57: 			temp = -1;
    58: 			tempForGenZero = generations[ 0 ];
    59: 			for ( int ind = 1; ind < generations.length; ind++ )
    60: 			{
    61: 				generations[ ind -1 ] = temp;
    62: 				temp = generations[ ind ];
    63: 				generations[ ind -1 ] = generations[ ind ];
    64: 			}
    65: 			generations[ bornGenInd ] = tempForGenZero;
    66: 			generations[ postBirthGenInd ] += tempForGenZero;
    67: 		}
    68: 
    69: 		if ( testing )
    70: 			for ( int ind = 0; ind < generations.length; ind++ )
    71: 				System.out.println( "pop "+ ind +" is "+ generations[ ind ] );
    72: 
    73: 		long finalPopulation = 0;
    74: 		for ( int ind = 0; ind < generations.length; ind++ )
    75: 			finalPopulation += generations[ ind ];
    76: 		System.out.println( "\tpopulation "+ finalPopulation );
    77: 	}
    78: 
    79: 
    80: }
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