some-advent-of-code: f0a02e3744d47cbaba7a69413a19e3741ace14db

     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 Exercise200301
    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: 		Point slope = new Point( 3, 1 );
    42: 		int validCount = treesInPath( fileLines, slope );
    43: 		System.out.println( here +"input has "+ validCount +" valid trees" );
    44: 	}
    45: 
    46: 
    47: 	private static int treesInPath(
    48: 			List<String> map,
    49: 			Point slope
    50: 	) {
    51: 		final String here = "e20031.m ";
    52: 		int trees = 0, times = 500;
    53: 		for ( Point ind = new Point( 0, 0 );
    54: 				ind.y < map.size() && times > 0;
    55: 				ind = nextPosition( map, ind, slope ) )
    56: 		{
    57: 			char collideWith = map.get( ind.y ).charAt( ind.x );
    58: 			if ( collideWith == tree )
    59: 			{
    60: 				trees += 1;			
    61: 	System.out.println( here +"tree at "+ ind );
    62: 			}
    63: 			times--;
    64: 		}
    65: if ( times == 0 )
    66: 	System.out.println( here +"quit by count, " );
    67: 		return trees;
    68: 	}
    69: 
    70: 
    71: 	private static Point nextPosition(
    72: 			List<String> map,
    73: 			Point ind,
    74: 			Point slope
    75: 	) {
    76: 		int nextY = ind.y + slope.y;
    77: 		int nextX = ind.x + slope.x;
    78: 		if ( nextX >= map.get( 0 ).length() )
    79: 		{
    80: 			nextX = nextX - map.get( 0 ).length();
    81: 		}
    82: 		ind.setLocation( nextX, nextY );
    83: 		return ind;
    84: 	}
    85: 
    86: }
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