some-advent-of-code: 1b66c53032a5657d02dfe2a2ebaa3226cc93315c

     1: 
     2: import java.awt.Point;
     3: import java.io.IOException;
     4: import java.nio.file.Files;
     5: import java.nio.file.InvalidPathException;
     6: import java.nio.file.Path;
     7: import java.nio.file.Paths;
     8: import java.util.HashSet;
     9: import java.util.LinkedList;
    10: import java.util.List;
    11: import java.util.Map;
    12: import java.util.Set;
    13: import java.util.TreeMap;
    14: 
    15: public class Exercise200302
    16: {
    17: 	private static final char tree = '#', ground = '.';
    18: 
    19: 	public static void main( String args[] )
    20: 	{
    21: 		final String here = "e20011.m ";
    22: 		if ( args.length < 1 )
    23: 		{
    24: 			throw new RuntimeException( here +"add a filename argument" );
    25: 		}
    26: 		String userSaysFile = args[ 0 ];
    27: 		List<String> fileLines = new LinkedList<>();
    28: 		try
    29: 		{
    30: 			Path where = Paths.get( userSaysFile );
    31: 			fileLines = Files.readAllLines( where );
    32: 		}
    33: 		catch ( IOException | InvalidPathException ie )
    34: 		{
    35: 			System.err.println( here +"couldn't read file "+ userSaysFile +" because "+ ie );
    36: 			return;
    37: 		}
    38: 		/*
    39: 		- interpretation of spec -
    40: 		*/
    41: 		List<Point> directions = new LinkedList<>();
    42: 		directions.add( new Point( 1, 1 ) );
    43: 		directions.add( new Point( 3, 1 ) );
    44: 		directions.add( new Point( 5, 1 ) );
    45: 		directions.add( new Point( 7, 1 ) );
    46: 		directions.add( new Point( 1, 2 ) );
    47: 		int validCount = 1;
    48: 		for ( Point slope : directions )
    49: 		{
    50: 			validCount *= treesInPath( fileLines, slope );
    51: 		}
    52: 		System.out.println( here +"input has "+ validCount +" valid trees" );
    53: 	}
    54: 
    55: 
    56: 	private static int treesInPath(
    57: 			List<String> map,
    58: 			Point slope
    59: 	) {
    60: 		final String here = "e20031.m ";
    61: 		int trees = 0, times = 500;
    62: 		for ( Point ind = new Point( 0, 0 );
    63: 				ind.y < map.size() && times > 0;
    64: 				ind = nextPosition( map, ind, slope ) )
    65: 		{
    66: 			char collideWith = map.get( ind.y ).charAt( ind.x );
    67: 			if ( collideWith == tree )
    68: 			{
    69: 				trees += 1;			
    70: 	System.out.println( here +"tree at "+ ind );
    71: 			}
    72: 			times--;
    73: 		}
    74: if ( times == 0 )
    75: 	System.out.println( here +"quit by count, " );
    76: 		return trees;
    77: 	}
    78: 
    79: 
    80: 	private static Point nextPosition(
    81: 			List<String> map,
    82: 			Point ind,
    83: 			Point slope
    84: 	) {
    85: 		int nextY = ind.y + slope.y;
    86: 		int nextX = ind.x + slope.x;
    87: 		if ( nextX >= map.get( 0 ).length() )
    88: 		{
    89: 			nextX = nextX - map.get( 0 ).length();
    90: 		}
    91: 		ind.setLocation( nextX, nextY );
    92: 		return ind;
    93: 	}
    94: 
    95: }
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