2021 Day 14 Complete!

2021/day14/main.go

@@ -0,0 +1,108 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+var template string
+var insertions map[string]string
+
+func main() {
+	insertions = make(map[string]string)
+	inp := h.StdinToStringSlice()
+	template = inp[0]
+	for i := 2; i < len(inp); i++ {
+		pts := strings.Split(inp[i], " -> ")
+		insertions[pts[0]] = pts[1]
+	}
+	part1(template)
+	fmt.Println()
+	part2(template)
+}
+
+func transform(inp string) string {
+	var ret string
+	for i := 0; i < len(inp)-1; i++ {
+		pair := inp[i : i+2]
+		ret = ret + string(inp[i]) + insertions[pair]
+	}
+	ret = ret + string(inp[len(inp)-1])
+	return ret
+}
+
+func part1(inp string) {
+	for i := 0; i < 10; i++ {
+		inp = transform(inp)
+	}
+	countMap := make(map[byte]int)
+	for i := range inp {
+		countMap[inp[i]]++
+	}
+	var mostCommon, leastCommon byte
+	mostCount := h.MIN_INT
+	leastCount := h.MAX_INT
+	for k, v := range countMap {
+		if v > mostCount {
+			mostCount = v
+			mostCommon = k
+		}
+		if v < leastCount {
+			leastCount = v
+			leastCommon = k
+		}
+	}
+	fmt.Println("# Part 1")
+	fmt.Printf("Most Common: %s (%d)\n", string(mostCommon), mostCount)
+	fmt.Printf("Least Common: %s (%d)\n", string(leastCommon), leastCount)
+	fmt.Println("Answer", (mostCount - leastCount))
+}
+
+func part2Transform(pairs map[string]int) map[string]int {
+	ret := make(map[string]int)
+	for k, v := range pairs {
+		add := insertions[k]
+		p1, p2 := string(k[0])+add, add+string(k[1])
+		ret[p1] += v
+		ret[p2] += v
+	}
+	return ret
+}
+
+func part2(inp string) {
+	// So the obvious way doesn't work for this many steps.
+	// Let's try just dealing with pairs.
+	pairs := make(map[string]int)
+	for i := 0; i < len(inp)-1; i++ {
+		pair := inp[i : i+2]
+		pairs[pair]++
+	}
+	for i := 0; i < 40; i++ {
+		pairs = part2Transform(pairs)
+	}
+	countMap := make(map[byte]int)
+	for k, v := range pairs {
+		countMap[k[0]] = countMap[k[0]] + v
+	}
+	countMap[inp[len(inp)-1]]++
+
+	var mostCommon, leastCommon byte
+	mostCount := h.MIN_INT
+	leastCount := h.MAX_INT
+	for k, v := range countMap {
+		if v > mostCount {
+			mostCount = v
+			mostCommon = k
+		}
+		if v < leastCount {
+			leastCount = v
+			leastCommon = k
+		}
+	}
+	fmt.Println("# Part 2")
+	fmt.Printf("Most Common: %s (%d)\n", string(mostCommon), mostCount)
+	fmt.Printf("Least Common: %s (%d)\n", string(leastCommon), leastCount)
+	fmt.Println("Answer", (mostCount - leastCount))
+}