2024 Day 15 Complete!

2024/day15/main.go

@@ -0,0 +1,229 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	fmt.Println()
+	part2(inp)
+}
+
+func part1(inp []string) {
+	fmt.Println("# Part 1")
+	m, dirs := parseInput(inp)
+	for i := range dirs {
+		bot, _ := m.FindFirst('@')
+		move(m, bot, dirs[i])
+	}
+	crates := m.FindAll('O')
+	var total int
+	for i := range crates {
+		add := (crates[i].Y*100 + crates[i].X)
+		total = total + add
+	}
+	fmt.Println("GPS Sum:", total)
+}
+
+func part2(inp []string) {
+	fmt.Println("# Part 2")
+	m, dirs := parseInput2(inp)
+	for i := range dirs {
+		bot, _ := m.FindFirst('@')
+		move(m, bot, dirs[i])
+	}
+	crates := m.FindAll('[')
+	var total int
+	for i := range crates {
+		add := (crates[i].Y*100 + crates[i].X)
+		total = total + add
+	}
+	fmt.Println("GPS Sum:", total)
+}
+
+func move(m h.CoordByteMap, orig h.Coordinate, dir byte) bool {
+	if !canMove(m, orig, dir) {
+		return false
+	}
+	oB := m.Get(orig)
+	if dir == '^' || dir == 'v' {
+		switch oB {
+		case ']':
+			return moveCrate(m, orig.West(), dir)
+		case '[':
+			return moveCrate(m, orig, dir)
+		}
+	}
+	var moveTo h.Coordinate
+	switch dir {
+	case '^':
+		moveTo = orig.North()
+	case '>':
+		moveTo = orig.East()
+	case 'v':
+		moveTo = orig.South()
+	case '<':
+		moveTo = orig.West()
+	}
+	dest := m.Get(moveTo)
+	if dest == '#' {
+		// A wall, can't move
+		return false
+	} else if dest != '.' {
+		// Not a wall, but not empty, can we push it?
+		if !move(m, moveTo, dir) {
+			return false
+		}
+		// Fall through
+	}
+	m.Put(moveTo, oB)
+	m.Put(orig, '.')
+	return true
+}
+
+func moveCrate(m h.CoordByteMap, orig h.Coordinate, dir byte) bool {
+	if !canMoveCrate(m, orig, dir) {
+		return false
+	}
+	var moveTo h.Coordinate
+	switch dir {
+	case '^':
+		moveTo = orig.North()
+	case 'v':
+		moveTo = orig.South()
+	}
+	destW, destE := m.Get(moveTo), m.Get(moveTo.East())
+	if destW == '#' || destE == '#' {
+		// A wall, can't move
+		return false
+	} else {
+		if destW != '.' && !move(m, moveTo, dir) {
+			return false
+		}
+		// Check other half of crate
+		if (destE != '.' && destE != ']') && !move(m, moveTo.East(), dir) {
+			return false
+		}
+		// Fall through
+	}
+	m.Put(moveTo, '[')
+	m.Put(moveTo.East(), ']')
+	m.Put(orig, '.')
+	m.Put(orig.East(), '.')
+	return true
+}
+
+func canMove(m h.CoordByteMap, orig h.Coordinate, dir byte) bool {
+	oB := m.Get(orig)
+	if dir == '^' || dir == 'v' {
+		switch oB {
+		case ']':
+			return canMoveCrate(m, orig.West(), dir)
+		case '[':
+			return canMoveCrate(m, orig, dir)
+		}
+	}
+	var moveTo h.Coordinate
+	switch dir {
+	case '^':
+		moveTo = orig.North()
+	case '>':
+		moveTo = orig.East()
+	case 'v':
+		moveTo = orig.South()
+	case '<':
+		moveTo = orig.West()
+	}
+	dest := m.Get(moveTo)
+	if dest == '#' {
+		// A wall, can't move
+		return false
+	} else if dest != '.' {
+		// Not a wall, but not empty, can we push it?
+		if !canMove(m, moveTo, dir) {
+			return false
+		}
+		// Fall through
+	}
+	// can move
+	return true
+}
+
+func canMoveCrate(m h.CoordByteMap, orig h.Coordinate, dir byte) bool {
+	var moveTo h.Coordinate
+	switch dir {
+	case '^':
+		moveTo = orig.North()
+	case 'v':
+		moveTo = orig.South()
+	}
+	destW, destE := m.Get(moveTo), m.Get(moveTo.East())
+
+	if destW == '#' || destE == '#' {
+		// A wall, can't move
+		return false
+	} else {
+		if destW != '.' && !canMove(m, moveTo, dir) {
+			return false
+		}
+		// Check other half of crate
+		if destE != '.' && !canMove(m, moveTo.East(), dir) {
+			return false
+		}
+		// Fall through
+	}
+	// can move
+	return true
+}
+
+func parseInput(inp []string) (h.CoordByteMap, []byte) {
+	var m h.CoordByteMap
+	var dirs []byte
+	var inDirs bool
+	for i := range inp {
+		if inDirs {
+			dirs = append(dirs, []byte(inp[i])...)
+		} else {
+			if inp[i] == "" {
+				m = h.StringSliceToCoordByteMap(inp[:i])
+				inDirs = true
+			}
+		}
+	}
+	return m, dirs
+}
+
+func parseInput2(inp []string) (h.CoordByteMap, []byte) {
+	// First modify the input
+	var m h.CoordByteMap
+	var newMap []string
+	var inDirs bool
+	var dirs []byte
+	for i := range inp {
+		if inDirs {
+			dirs = append(dirs, []byte(inp[i])...)
+		} else {
+			if inp[i] == "" {
+				m = h.StringSliceToCoordByteMap(newMap)
+				inDirs = true
+			}
+			var newLine []byte
+			for j := range inp[i] {
+				switch inp[i][j] {
+				case 'O':
+					newLine = append(newLine, []byte{'[', ']'}...)
+				case '@':
+					newLine = append(newLine, []byte{'@', '.'}...)
+				default:
+					newLine = append(newLine, []byte{inp[i][j], inp[i][j]}...)
+				}
+			}
+			newMap = append(newMap, string(newLine))
+		}
+	}
+	return m, dirs
+}