2023 Day 12 Complete!

2023/day12/main.go

@@ -0,0 +1,109 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	inp := h.StdinToStringSlice()
+	part1(inp)
+	fmt.Println()
+	part2(inp)
+}
+
+func part1(input []string) {
+	var records []string
+	var groups [][]int
+	for _, ln := range input {
+		pts := strings.Fields(ln)
+		records = append(records, pts[0])
+		var grp []int
+		for _, n := range strings.Split(pts[1], ",") {
+			grp = append(grp, h.Atoi(n))
+		}
+		groups = append(groups, grp)
+	}
+	var result int
+	for i := range records {
+		// Initialize cache for this row
+		cache := make(map[string]int)
+
+		// And solve the row
+		result += solveRow(0, 0, records[i], groups[i], cache)
+	}
+
+	fmt.Println("# Part 1")
+	fmt.Println(result)
+}
+
+func part2(input []string) {
+	var records []string
+	var groups [][]int
+	for _, ln := range input {
+		pts := strings.Fields(ln)
+		// Unfold the paper
+		pts[0] = fmt.Sprintf("%s?%s?%s?%s?%s", pts[0], pts[0], pts[0], pts[0], pts[0])
+		pts[1] = fmt.Sprintf("%s,%s,%s,%s,%s", pts[1], pts[1], pts[1], pts[1], pts[1])
+		records = append(records, pts[0])
+		var grp []int
+		for _, n := range strings.Split(pts[1], ",") {
+			grp = append(grp, h.Atoi(n))
+		}
+		groups = append(groups, grp)
+	}
+
+	var result int
+	for i := range records {
+		// Initialize cache for this row
+		cache := make(map[string]int)
+
+		// And solve the row
+		result += solveRow(0, 0, records[i], groups[i], cache)
+	}
+
+	fmt.Println("# Part 2")
+	fmt.Println(result)
+}
+
+func ck(i, j int) string { return fmt.Sprintf("%d_%d", i, j) }
+
+func solveRow(rbIdx, groupIdx int, record string, group []int, cache map[string]int) int {
+	if rbIdx >= len(record) {
+		if groupIdx < len(group) {
+			return 0
+		}
+		return 1
+	}
+	if v, ok := cache[ck(rbIdx, groupIdx)]; ok {
+		return v
+	}
+	res := 0
+	if record[rbIdx] == '.' {
+		res = solveRow(rbIdx+1, groupIdx, record, group, cache)
+	} else {
+		if record[rbIdx] == '?' {
+			res += solveRow(rbIdx+1, groupIdx, record, group, cache)
+		}
+		if groupIdx < len(group) {
+			count := 0
+			for k := rbIdx; k < len(record); k++ {
+				if count > group[groupIdx] || record[k] == '.' || count == group[groupIdx] && record[k] == '?' {
+					break
+				}
+				count += 1
+			}
+			if count == group[groupIdx] {
+				if rbIdx+count < len(record) && record[rbIdx+count] != '#' {
+					res += solveRow(rbIdx+count+1, groupIdx+1, record, group, cache)
+				} else {
+					res += solveRow(rbIdx+count, groupIdx+1, record, group, cache)
+				}
+			}
+		}
+	}
+	cache[ck(rbIdx, groupIdx)] = res
+	return res
+}