2925: day 2 (quite bad version)

AdventOfCode2025/day2/day2.go

@@ -0,0 +1,121 @@
+package main
+
+import (
+	"fmt"
+	"math"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type Range struct {
+	Lower int
+	Upper int
+}
+
+// 10 = 1, 2, 5
+func factorsWithoutNum(num int) []int {
+	factors := make([]int, 0)
+
+	for i := 1; i < num; i++ {
+		if num%i == 0 {
+			factors = append(factors, i)
+		}
+	}
+
+	return factors
+}
+
+func isSliceAllEqual(s []int) bool {
+	if len(s) == 0 {
+		return true
+	}
+
+	firstItem := s[0]
+	for _, i := range s {
+		if firstItem != i {
+			return false
+		}
+	}
+
+	return true
+}
+
+func testNumber(num int) bool {
+	digits := int(math.Floor(math.Log10(float64(num)))) + 1
+
+	factors := factorsWithoutNum(digits)
+	for _, chunkSize := range factors {
+		nums := make([]int, 0)
+		for i := chunkSize; i <= digits; i += chunkSize {
+			divisor := int(math.Pow10(i))
+			remainderDivisor := int(math.Pow10(i - chunkSize))
+
+			remainder := num % divisor
+			remainder = remainder / remainderDivisor
+
+			nums = append(nums, remainder)
+		}
+
+		if isSliceAllEqual(nums) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func main() {
+	lines, err := os.ReadFile("./input.txt")
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+
+	trimmedString := strings.TrimSuffix(string(lines), "\n")
+
+	splitLines := strings.Split(trimmedString, ",")
+
+	ranges := make([]Range, len(splitLines))
+	for i, line := range splitLines {
+		stringRange := strings.Split(line, "-")
+
+		lower, errLower := strconv.Atoi(stringRange[0])
+		upper, errUpper := strconv.Atoi(stringRange[1])
+
+		if errLower != nil || errUpper != nil {
+			fmt.Println(errLower, errUpper)
+			os.Exit(1)
+		}
+
+		ranges[i] = Range{lower, upper}
+	}
+
+	// log10 -> find number of digits.
+
+	part1 := 0
+	part2 := 0
+
+	for _, r := range ranges {
+		for i := r.Lower; i <= r.Upper; i++ {
+			base10 := math.Log10(float64(i))
+			exp := int(math.Floor(base10)) + 1
+
+			divisor := int(math.Pow10(exp / 2))
+
+			upperHalf := i / divisor
+			lowerHalf := i % divisor
+
+			if upperHalf == lowerHalf {
+				part1 += i
+			}
+
+			if testNumber(i) {
+				part2 += i
+			}
+		}
+	}
+
+	fmt.Printf("Part 1: %d\n", part1)
+	fmt.Printf("Part 2: %d\n", part2)
+}