2025: 01

.gitignore

@@ -0,0 +1 @@
+**.txt

2025/01/main.go

@@ -0,0 +1,75 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+func main() {
+	sum := 50
+	res1 := 0
+	res2 := 0
+
+	file, err := os.Open("./input.txt")
+	//file, err := os.Open("./test.txt")
+
+	if err != nil {
+		return
+	}
+
+	defer file.Close()
+
+	re := regexp.MustCompile("(L|R)(\\w+)")
+
+	scanner := bufio.NewScanner(file)
+
+	for scanner.Scan() {
+		// Since re : "(L|R)(\w+)", we can parse it as the following i
+		i := 0
+		{
+			m := re.FindStringSubmatch(scanner.Text())
+
+			i, _ = strconv.Atoi(m[2])
+
+			if m[1] == "L" {
+				i *=  -1
+			}
+		}
+
+		// Handle sum +=i  as mod(100) and work w/res2
+		{
+			// Avoid counting rebundant match
+			if sum == 0 && i < 0 {
+				res2 -= 1
+			}
+
+			sum += i
+
+			for sum < 0  {
+				sum += 100
+				res2 += 1
+			}
+			for sum > 100 {
+				sum -= 100
+				res2 += 1
+			}
+			if sum == 100 {
+				sum -= 100
+			}
+		}
+
+		// work w/res1
+		if sum == 0 {
+			res1 += 1
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return
+	}
+
+	fmt.Println(res1, res1+res2)
+}

2025/01/test.txt

@@ -0,0 +1,10 @@
+L68
+L30
+R48
+L5
+R60
+L55
+L1
+L99
+R14
+L82

2025/Makefile

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+INPUT = \
+	01/input.txt 
+
+.SUFFIXES: .txt
+
+$(INPUT):
+	curl "https://adventofcode.com/2025/day/`echo $@|sed -r 's,^0*(\w+/input).txt$$,\1,'`" -H 'Cookie: session=$(SESSION)' > $@