day 14

14/main.go

@@ -0,0 +1,157 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"time"
+)
+
+func mustAtoi(line string) int {
+	i, _ := strconv.Atoi(line)
+	return i
+}
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	polymer := map[string]int{}
+
+	// initial state
+	scanner.Scan()
+	initial := scanner.Text()
+	for i := 0; i < len(initial)-1; i++ {
+		pair := string(initial[i]) + string(initial[i+1])
+		polymer[pair]++
+	}
+
+	// eat empty line
+	scanner.Scan()
+
+	rulemap := map[string][]string{}
+	for scanner.Scan() {
+		rule := strings.Split(scanner.Text(), " -> ")
+		rulemap[rule[0]] = []string{
+			string(rule[0][0]) + rule[1],
+			rule[1] + string(rule[0][1]),
+		}
+	}
+
+	// apply rules
+	for i := 0; i < 10; i++ {
+		newPolymer := map[string]int{}
+		for p, c := range polymer {
+			newPolymer[rulemap[p][0]] += c
+			newPolymer[rulemap[p][1]] += c
+		}
+		polymer = newPolymer
+	}
+
+	// count elements
+	count := map[string]int{}
+	for p, c := range polymer {
+		count[string(p[0])] += c
+		count[string(p[1])] += c
+	}
+
+	// find max and min
+	max, min := 0, 0
+	for _, c := range count {
+		if c > max {
+			max = c
+		}
+		if c < min || min == 0 {
+			min = c
+		}
+	}
+
+	// handle rounding
+	if (max-min)%2 == 1 {
+		fmt.Println((max-min)/2 + 1)
+	} else {
+		fmt.Println((max - min) / 2)
+	}
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+
+	polymer := map[string]int{}
+
+	// initial state
+	scanner.Scan()
+	initial := scanner.Text()
+	for i := 0; i < len(initial)-1; i++ {
+		pair := string(initial[i]) + string(initial[i+1])
+		polymer[pair]++
+	}
+
+	// eat empty line
+	scanner.Scan()
+
+	rulemap := map[string][]string{}
+	for scanner.Scan() {
+		rule := strings.Split(scanner.Text(), " -> ")
+		rulemap[rule[0]] = []string{
+			string(rule[0][0]) + rule[1],
+			rule[1] + string(rule[0][1]),
+		}
+	}
+
+	// apply rules
+	for i := 0; i < 40; i++ {
+		newPolymer := map[string]int{}
+		for p, c := range polymer {
+			newPolymer[rulemap[p][0]] += c
+			newPolymer[rulemap[p][1]] += c
+		}
+		polymer = newPolymer
+	}
+
+	// count elements
+	count := map[string]int{}
+	for p, c := range polymer {
+		count[string(p[0])] += c
+		count[string(p[1])] += c
+	}
+
+	// find max and min
+	max, min := 0, 0
+	for _, c := range count {
+		if c > max {
+			max = c
+		}
+		if c < min || min == 0 {
+			min = c
+		}
+	}
+
+	// handle rounding
+	if (max-min)%2 == 1 {
+		fmt.Println((max-min)/2 + 1)
+	} else {
+		fmt.Println((max - min) / 2)
+	}
+}