2024 day 12 Complete!

2024/day12/main.go

@@ -0,0 +1,162 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToCoordMap()
+	part1(inp)
+	fmt.Println("")
+	part2(inp)
+}
+
+func part1(inp h.CoordByteMap) {
+	fmt.Println("# Part 1")
+	var total int
+	trackedPlots := make(map[h.Coordinate]bool)
+	for y := inp.TLY; y <= inp.BRY; y++ {
+		for x := inp.TLX; x <= inp.BRX; x++ {
+			c := h.Coordinate{X: x, Y: y}
+			if trackedPlots[c] {
+				continue
+			}
+			plant := inp.Get(c)
+			region := findRegion(inp, c, make(map[h.Coordinate]bool))
+			area := len(region)
+			var perimeter int
+			for k := range region {
+				trackedPlots[k] = true
+				for _, chk := range []h.Coordinate{k.North(), k.East(), k.South(), k.West()} {
+					if inp.Get(chk) != plant {
+						perimeter++
+					}
+				}
+			}
+			total = total + (area * perimeter)
+		}
+	}
+	fmt.Println("Total Price:", total)
+}
+
+func part2(inp h.CoordByteMap) {
+	fmt.Println("# Part 2")
+	var total int
+	trackedPlots := make(map[h.Coordinate]bool)
+	for y := inp.TLY; y <= inp.BRY; y++ {
+		for x := inp.TLX; x <= inp.BRX; x++ {
+			c := h.Coordinate{X: x, Y: y}
+			if trackedPlots[c] {
+				continue
+			}
+			region := findRegion(inp, c, make(map[h.Coordinate]bool))
+			area := len(region)
+			for k := range region {
+				trackedPlots[k] = true
+			}
+			sides := findSides(region)
+			total = total + (area * sides)
+		}
+	}
+	fmt.Println("Total Price:", total)
+}
+
+func findRegion(inp h.CoordByteMap, start h.Coordinate, checked map[h.Coordinate]bool) map[h.Coordinate]bool {
+	ret := make(map[h.Coordinate]bool)
+	bt := inp.Get(start)
+	ret[start] = true
+	for _, chk := range []h.Coordinate{start.North(), start.East(), start.South(), start.West()} {
+		if checked[chk] {
+			continue
+		}
+		if inp.Get(chk) == bt {
+			checked[chk] = true
+			ret[chk] = true
+			for k := range findRegion(inp, chk, checked) {
+				ret[k] = true
+			}
+		}
+	}
+	return ret
+}
+
+var (
+	N  = h.Coordinate{X: 0, Y: -1}
+	NE = h.Coordinate{X: 1, Y: -1}
+	E  = h.Coordinate{X: 1, Y: 0}
+	SE = h.Coordinate{X: 1, Y: 1}
+	S  = h.Coordinate{X: 0, Y: 1}
+	SW = h.Coordinate{X: -1, Y: 1}
+	W  = h.Coordinate{X: -1, Y: 0}
+	NW = h.Coordinate{X: -1, Y: -1}
+)
+
+func findSides(region map[h.Coordinate]bool) int {
+	var sides int
+	for chk := range region {
+		sides = sides + checkForExteriorCorner(chk, region)
+		sides = sides + checkForInteriorCorner(chk, region)
+	}
+	return sides
+}
+
+// checkForExteriorCorner returns how many exterior corners 'chk' is a part of
+func checkForExteriorCorner(chk h.Coordinate, region map[h.Coordinate]bool) int {
+	var ret int
+	// Check orthoganal neighbor pairs (N/E, E/S, S/W, W/N) for an exterior corner
+	if checkDiff(chk, N, region) {
+		if checkDiff(chk, E, region) {
+			ret++
+		}
+		if checkDiff(chk, W, region) {
+			ret++
+		}
+	}
+	if checkDiff(chk, S, region) {
+		if checkDiff(chk, E, region) {
+			ret++
+		}
+		if checkDiff(chk, W, region) {
+			ret++
+		}
+	}
+	return ret
+}
+
+// checkForInteriorCorner returns how many interior corners 'chk' is a part of
+func checkForInteriorCorner(chk h.Coordinate, region map[h.Coordinate]bool) int {
+	var ret int
+	// Check for interior corner (N/E != NE, E/S != SE, S/W != SW, W/N != NW)
+	if checkDiff(chk, NE, region) {
+		if checkSame(chk, N, region) && checkSame(chk, E, region) {
+			ret++
+		}
+	}
+	if checkDiff(chk, SE, region) {
+		if checkSame(chk, S, region) && checkSame(chk, E, region) {
+			ret++
+		}
+	}
+	if checkDiff(chk, SW, region) {
+		if checkSame(chk, S, region) && checkSame(chk, W, region) {
+			ret++
+		}
+	}
+	if checkDiff(chk, NW, region) {
+		if checkSame(chk, N, region) && checkSame(chk, W, region) {
+			ret++
+		}
+	}
+	return ret
+}
+
+func checkDiff(chk, dir h.Coordinate, region map[h.Coordinate]bool) bool {
+	return !checkSame(chk, dir, region)
+}
+
+func checkSame(chk, dir h.Coordinate, region map[h.Coordinate]bool) bool {
+	_, ok := region[chk.Add(dir)]
+	return ok
+}