Day 1 Part 2

1/solve_1.go

@@ -8,36 +8,35 @@ import (
 	"strconv"
 )
 
-
-func main()  {
-	nb_occ_zero  := 0
+func main() {
+	nb_occ_zero := 0
 	lock_num := 50
 	direction := 1
-	var nb_ticks int;
-	var instruction string 
+	var nb_ticks int
+	var instruction string
 	f, err := os.Open("1/input")
-	if err != nil{
+	if err != nil {
 		log.Fatal(err)
 	}
 	defer f.Close()
 	scanner := bufio.NewScanner(f)
 
 	// We read input line by line
-	for scanner.Scan(){
+	for scanner.Scan() {
 		instruction = scanner.Text()
-		switch (instruction[0]){
-			case 'L':
+		switch instruction[0] {
+		case 'L':
 			direction = -1
-			case 'R':
+		case 'R':
 			direction = 1
-			default:
+		default:
 			panic("unrecognized instruction")
 		}
 		nb_ticks, err = strconv.Atoi(instruction[1:])
-		if err != nil{
+		if err != nil {
 			log.Fatal(err)
 		}
-		lock_num = (lock_num + direction * nb_ticks) % 100
+		lock_num = (lock_num + direction*nb_ticks) % 100
 		if lock_num < 0 {
 			lock_num = lock_num + 100
 		}

1/solve_2.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"log"
+	"math"
+	"os"
+	"strconv"
+)
+
+func main() {
+	nb_occ_zero, lock_num := 0, 50
+	var direction, nb_ticks, prev_lock_num, nb_cycles int
+	var instruction string
+
+	f, _ := os.Open("1/input")
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		instruction = scanner.Text()
+		switch instruction[0] {
+		case 'L':
+			direction = -1
+		case 'R':
+			direction = 1
+		default:
+			panic("unrecognized instruction")
+		}
+
+		nb_ticks, _ = strconv.Atoi(instruction[1:])
+		prev_lock_num = lock_num
+
+		lock_num, nb_cycles = (lock_num+direction*nb_ticks)%100, (direction*nb_ticks)/100
+		if lock_num < 0 {
+			lock_num += 100
+		}
+		
+		nb_occ_zero += int(math.Abs(float64(nb_cycles)))
+
+		if prev_lock_num == 0 {
+			continue
+		}
+
+		if lock_num == 0 {
+			nb_occ_zero++
+		} else if direction == -1 && lock_num > prev_lock_num {
+			nb_occ_zero++
+		} else if direction == 1 && lock_num < prev_lock_num {
+			nb_occ_zero++
+		}
+
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Println(nb_occ_zero)
+}

README.md

@@ -20,7 +20,7 @@ Each day's folder is named after the day number (`1` to `12`). Inside each folde
 
 | Day | Part 1 | Part 2 |
 |-----|--------|--------|
-| 1   | ✅     | ⬜     |
+| 1   | ✅     | ✅     |
 | 2   | ⬜     | ⬜     |
 | 3   | ⬜     | ⬜     |
 | 4   | ⬜     | ⬜     |