AOC 2025 Day 1 -> 4 solutions

2025/01/kylepritchard.v

@@ -0,0 +1,59 @@
+module main
+
+import os
+import strconv
+
+fn main() {
+	codes := os.read_file('rotations.input') or { panic('Failed to read file') }
+
+	mut start := 50
+	mut count := 0
+	mut count2 := 0
+
+	for line in codes.split_into_lines() {
+		if line.len == 0 {
+			continue
+		}
+
+		if line[0] == `L` {
+			move_str := line[1..].trim_space()
+			mut move := strconv.atoi(move_str) or { 0 }
+
+			for move > 0 {
+				start--
+				if start == 0 {
+					count2++
+				}
+				if start == -1 {
+					start = 99
+				}
+				move--
+			}
+
+			if start == 0 {
+				count++
+			}
+		} else {
+			move_str := line[1..].trim_space()
+			mut move := strconv.atoi(move_str) or { 0 }
+
+			for move > 0 {
+				start++
+				if start == 100 {
+					start = 0
+				}
+				if start == 0 {
+					count2++
+				}
+				move--
+			}
+
+			if start == 0 {
+				count++
+			}
+		}
+	}
+
+	println('Part 1: ${count}')
+	println('Part 2: ${count2}')
+}

2025/02/kylepritchard.v

@@ -0,0 +1,85 @@
+module main
+
+import os
+import strconv
+
+fn has_exact_two_halves(s string) bool {
+	if s.len % 2 != 0 {
+		return false
+	}
+	half := s.len / 2
+	return s[0..half] == s[half..]
+}
+
+fn has_repeating_pattern(s string) bool {
+	for pattern_len in 1 .. s.len / 2 + 1 {
+		if s.len % pattern_len != 0 {
+			continue
+		}
+
+		pattern := s[0..pattern_len]
+		mut matches := true
+
+		repetitions := s.len / pattern_len
+		for rep in 1 .. repetitions {
+			start := rep * pattern_len
+			end := start + pattern_len
+			if s[start..end] != pattern {
+				matches = false
+				break
+			}
+		}
+
+		if matches {
+			return true
+		}
+	}
+	return false
+}
+
+fn main() {
+	content := os.read_file('ids.input') or { panic('Failed to read file: ${err}') }
+
+	ids := content.split(',')
+
+	mut sum1 := i64(0)
+	mut sum2 := i64(0)
+
+	for id in ids {
+		if id.len == 0 {
+			continue
+		}
+
+		range_parts := id.split('-')
+
+		start_str := range_parts[0].trim_space()
+		end_str := range_parts[1].trim_space()
+
+		start := strconv.parse_int(start_str, 10, 64) or {
+			eprintln('Start number isn\'t valid: "${id}"')
+			continue
+		}
+
+		end := strconv.parse_int(end_str, 10, 64) or {
+			eprintln('End number isn\'t valid: "${id}"')
+			continue
+		}
+
+		for num in start .. end + 1 {
+			num_str := num.str()
+
+			// Part 1
+			if has_exact_two_halves(num_str) {
+				sum1 += num
+			}
+
+			// Part 2
+			if has_repeating_pattern(num_str) {
+				sum2 += num
+			}
+		}
+	}
+
+	println('Part 1: ${sum1}')
+	println('Part 2: ${sum2}')
+}

2025/03/kylepritchard.v

@@ -0,0 +1,71 @@
+module main
+
+import os
+import strconv
+
+fn max_sequence(s string, k int) string {
+	to_remove := s.len - k
+	mut remove_left := to_remove
+
+	mut stack := []u8{len: 0, cap: s.len}
+
+	for i in 0 .. s.len {
+		c := s[i]
+		for stack.len > 0 && remove_left > 0 && stack[stack.len - 1] < c {
+			stack.delete_last()
+			remove_left--
+		}
+		stack << c
+	}
+
+	if remove_left > 0 {
+		stack = stack[..stack.len - remove_left].clone()
+	}
+
+	if stack.len > k {
+		stack = stack[..k].clone()
+	}
+
+	return stack.bytestr()
+}
+
+fn main() {
+	content := os.read_file('banks.input') or { panic('Failed to read file: ${err}') }
+	lines := content.split_into_lines()
+
+	// Part 1
+	mut total_joltage := i64(0)
+	for line in lines {
+		if line.len == 0 {
+			continue
+		}
+
+		seq := max_sequence(line, 2)
+		if seq.len == 0 {
+			continue
+		}
+
+		num := strconv.parse_int(seq, 10, 64) or { 0 }
+		total_joltage += num
+	}
+
+	println('Part 1: ${total_joltage}')
+
+	// Part 2
+	total_joltage = 0
+	for line in lines {
+		if line.len == 0 {
+			continue
+		}
+
+		seq := max_sequence(line, 12)
+		if seq.len == 0 {
+			continue
+		}
+
+		num := strconv.parse_int(seq, 10, 64) or { 0 }
+		total_joltage += num
+	}
+
+	println('Part 2: ${total_joltage}')
+}

2025/04/kylepritchard.v

@@ -0,0 +1,159 @@
+module main
+
+import os
+
+struct Pos {
+	row int
+	col int
+}
+
+struct Offset {
+	dr int
+	dc int
+}
+
+fn count_adjacent(grid []u8, rows int, cols int, i int, j int, neighbors []Offset) int {
+	mut count := 0
+
+	for offset in neighbors {
+		ni := i + offset.dr
+		nj := j + offset.dc
+
+		if ni >= 0 && nj >= 0 && ni < rows && nj < cols { // inside grid
+			nidx := ni * cols + nj
+			if grid[nidx] == `@` {
+				count++
+				if count >= 4 {
+					break
+				}
+			}
+		}
+	}
+	return count
+}
+
+fn main() {
+	// Read input file
+	content := os.read_file('department.input') or { panic('Failed to read file: ${err}') }
+	lines := content.split_into_lines()
+
+	mut grid_lines := []string{}
+	for line in lines {
+		if line.len > 0 {
+			grid_lines << line
+		}
+	}
+
+	rows := grid_lines.len
+	cols := grid_lines[0].len
+
+	mut grid1 := []u8{len: rows * cols, cap: rows * cols}
+	mut grid2 := []u8{len: rows * cols, cap: rows * cols}
+
+	for i in 0 .. rows {
+		line := grid_lines[i]
+		row_start := i * cols
+		for j in 0 .. cols {
+			grid1[row_start + j] = line[j]
+			grid2[row_start + j] = line[j]
+		}
+	}
+
+	neighbors := [
+		Offset{-1, -1}, // diagonal above left
+		Offset{-1, 0}, // above
+		Offset{-1, 1}, // diagional above right
+		Offset{0, -1}, // left
+		Offset{0, 1}, // right
+		Offset{1, -1}, // diagonal below left
+		Offset{1, 0}, // below
+		Offset{1, 1}, // diagonal below right
+	]
+
+	// Part 1
+	mut part1_count := 0
+	for i in 0 .. rows {
+		row_start := i * cols
+		for j in 0 .. cols {
+			idx := row_start + j
+			if grid1[idx] == `@` {
+				adj_count := count_adjacent(grid1, rows, cols, i, j, neighbors)
+				if adj_count < 4 {
+					part1_count++
+				}
+			}
+		}
+	}
+
+	println('Part 1: ${part1_count}')
+
+	// Part 2
+	mut total_removed := 0
+	mut current_grid := grid2.clone()
+	mut changed := true
+
+	mut to_check := []Pos{cap: rows * cols}
+
+	for i in 0 .. rows {
+		for j in 0 .. cols {
+			to_check << Pos{i, j}
+		}
+	}
+
+	for changed {
+		changed = false
+		mut to_remove := []Pos{cap: to_check.len}
+		mut next_to_check := []Pos{cap: rows * cols}
+		mut modified := []bool{len: rows * cols, init: false}
+
+		for pos in to_check {
+			i := pos.row
+			j := pos.col
+			idx := i * cols + j
+
+			if current_grid[idx] != `@` {
+				continue
+			}
+
+			adj_count := count_adjacent(current_grid, rows, cols, i, j, neighbors)
+			if adj_count < 4 {
+				to_remove << pos
+			}
+		}
+
+		// Remove rolls
+		if to_remove.len > 0 {
+			changed = true
+			total_removed += to_remove.len
+
+			// Mark positions as removed and track their neighbors
+			for pos in to_remove {
+				i := pos.row
+				j := pos.col
+				idx := i * cols + j
+				current_grid[idx] = `.`
+				modified[idx] = true
+
+				// Add neighbors to next iteration's check list
+				for offset in neighbors {
+					ni := i + offset.dr
+					nj := j + offset.dc
+					if ni >= 0 && nj >= 0 && ni < rows && nj < cols {
+						nidx := ni * cols + nj
+						if !modified[nidx] {
+							modified[nidx] = true
+							next_to_check << Pos{ni, nj}
+						}
+					}
+				}
+			}
+
+			to_check = next_to_check.clone()
+		} else {
+			// No more to remove
+			break
+		}
+	}
+
+	println('Part 2: ${total_removed}')
+}

known/2025/01/kylepritchard.out

@@ -0,0 +1,2 @@
+Part 1: 3
+Part 2: 6

known/2025/02/kylepritchard.out

@@ -0,0 +1,2 @@
+Part 1: 1227775554
+Part 2: 4174379265

known/2025/03/kylepritchard.out

@@ -0,0 +1,2 @@
+Part 1: 357
+Part 2: 3121910778619

known/2025/04/kylepritchard.out

@@ -0,0 +1,2 @@
+Part 1: 13
+Part 2: 43