Solution for 12.1.

2018/internal/day12/plants.go

@@ -0,0 +1,80 @@
+package day12
+
+type Rule struct {
+	Positions [5]bool
+	Result    bool
+}
+
+func (r Rule) String() string {
+	res := ""
+	for _, p := range r.Positions {
+		res += plantString(p)
+	}
+	res += " => "
+	res += plantString(r.Result)
+	return res
+}
+
+func plantString(isPlant bool) string {
+	if isPlant {
+		return "#"
+	}
+	return "."
+}
+
+func getPlantBounds(plants map[int]bool) (int, int) {
+	keys := make([]int, len(plants))
+	i := 0
+	for key, _ := range plants {
+		keys[i] = key
+		i++
+	}
+
+	low := keys[0]
+	high := keys[0]
+	for _, key := range keys {
+		if key < low {
+			low = key
+		}
+		if key > high {
+			high = key
+		}
+	}
+
+	return low, high
+}
+
+func RunGeneration(plants map[int]bool, rules []*Rule) map[int]bool {
+	newGen := make(map[int]bool)
+
+	low, high := getPlantBounds(plants)
+
+	for i := low - 2; i < high+3; i++ {
+		for _, rule := range rules {
+			if checkRule(plants, rule, i) {
+				newGen[i] = rule.Result
+			}
+		}
+	}
+
+	return newGen
+}
+
+func checkRule(plants map[int]bool, rule *Rule, i int) bool {
+	for j := 0; j < 5; j++ {
+		if plants[i+j-2] != rule.Positions[j] {
+			return false
+		}
+	}
+	return true
+}
+
+func SumPlants(plants map[int]bool) int {
+	sum := 0
+	for key, value := range plants {
+		if value {
+			sum += key
+		}
+	}
+	return sum
+}