2025 day 3

Author: lucianoq

2025/3/Makefile

@@ -0,0 +1,20 @@
+input:
+	http "https://adventofcode.com/2025/day/3/input" "Cookie:session=${AOC_SESSION};" >input
+
+main1:
+	go build -o main1 main1.go common.go
+
+main2:
+	go build -o main2 main2.go common.go
+
+.PHONY: run1 run2 clean
+
+run1: main1 input
+	./main1 <input
+
+run2: main2 input
+	./main2 <input
+
+clean:
+	rm -f main1 main2 input
+

2025/3/common.go

@@ -0,0 +1,24 @@
+package main
+
+func findJolts(bank string, digits int) int {
+	output := 0
+	idx := -1
+	for i := digits; i > 0; i-- {
+		var jolts int
+		jolts, idx = findMax(bank, idx+1, len(bank)-i+1)
+		output = output*10 + jolts
+	}
+	return output
+}
+
+func findMax(list string, start, end int) (int, int) {
+	var maxJolts uint8
+	var idx int
+	for i := start; i < end; i++ {
+		if list[i] > maxJolts {
+			maxJolts = list[i]
+			idx = i
+		}
+	}
+	return int(maxJolts - '0'), idx
+}

2025/3/main1.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	total := 0
+	for scanner := bufio.NewScanner(os.Stdin); scanner.Scan(); {
+		total += findJolts(scanner.Text(), 2)
+	}
+	fmt.Println(total)
+}

2025/3/main2.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+)
+
+func main() {
+	total := 0
+	for scanner := bufio.NewScanner(os.Stdin); scanner.Scan(); {
+		total += findJolts(scanner.Text(), 12)
+	}
+	fmt.Println(total)
+}