day22: solve first part

Author: fxnn

day22/example1.txt

@@ -0,0 +1,10 @@
+15887950
+16495136
+527345
+704524
+1553684
+12683156
+11100544
+12249484
+7753432
+5908254

day22/example2.txt

@@ -0,0 +1,4 @@
+1
+10
+100
+2024

day22/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+
+	"github.com/fxnn/adventofcode2024/util"
+)
+
+func readInitialSecrets() []int {
+	var scanner = bufio.NewScanner(os.Stdin)
+
+	var secrets []int
+	for scanner.Scan() {
+		var line = scanner.Text()
+		secrets = append(secrets, util.Atoi(line))
+	}
+	if err := scanner.Err(); err != nil {
+		fmt.Fprintf(os.Stderr, "Error: %s\n", err)
+		os.Exit(1)
+	}
+
+	return secrets
+}
+
+func mixAndPrune(number, secret int) int {
+	return (number ^ secret) % 16777216
+}
+
+func calculateNextSecret(secret int) int {
+	var step1 = mixAndPrune(secret*64, secret)
+	var step2 = mixAndPrune(step1/32, step1)
+	var step3 = mixAndPrune(step2*2048, step2)
+	return step3
+}
+
+func main() {
+	var sum int
+	for _, initialSecret := range readInitialSecrets() {
+		var secret = initialSecret
+		for i := 0; i < 2000; i++ {
+			secret = calculateNextSecret(secret)
+		}
+		sum += secret
+		fmt.Printf("%d: %d\n", initialSecret, secret)
+	}
+	fmt.Printf("sum of secrets: %d\n", sum)
+}