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Day2.java
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Day2.java
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import java.util.List;
public class Day2 {
static char[][] GRID_PART1 = {
{ '1', '2', '3' },
{ '4', '5', '6' },
{ '7', '8', '9' } };
static char[][] GRID_PART2 = {
{ '\0', '\0', '1', '\0', '\0' },
{ '\0', '2', '3', '4', '\0' },
{ '5', '6', '7', '8', '9' },
{ '\0', 'A', 'B', 'C', '\0' },
{ '\0', '\0', 'D', '\0', '\0' } };
static String day2(List<String> rows, char[][] grid, int xStart, int yStart) {
int x = xStart;
int y = yStart;
int bound = grid.length - 1; // assume NxN grid
StringBuilder result = new StringBuilder(rows.size());
for (String r : rows) {
for (byte c : r.getBytes()) {
switch (c) {
case 'U':
if (x != 0 && '\0' != grid[x - 1][y])
x--;
break;
case 'D':
if (x != bound && '\0' != grid[x + 1][y])
x++;
break;
case 'L':
if (y != 0 && '\0' != grid[x][y - 1])
y--;
break;
case 'R':
if (y != bound && '\0' != grid[x][y + 1])
y++;
break;
}
}
result.append(grid[x][y]);
}
return result.toString();
}
public static void main(String[] args) {
List<String> input = Util.readInput("day2.input");
// Part 1 : 98575
System.out.println(day2(input, GRID_PART1, 1, 1));
// Part 2 : CD8D4
System.out.println(day2(input, GRID_PART2, 2, 0));
}
}