Completed 6-2

6-2/go.mod

@@ -0,0 +1,3 @@
+module git.home.dutchellie.nl/DutchEllie/adventofcode2021/6-2
+
+go 1.17

6-2/input

@@ -0,0 +1 @@
+4,1,3,2,4,3,1,4,4,1,1,1,5,2,4,4,2,1,2,3,4,1,2,4,3,4,5,1,1,3,1,2,1,4,1,1,3,4,1,2,5,1,4,2,2,1,1,1,3,1,5,3,1,2,1,1,1,1,4,1,1,1,2,2,1,3,1,3,1,3,4,5,1,2,2,1,1,1,4,1,5,1,3,1,3,4,1,3,2,3,4,4,4,3,4,5,1,3,1,3,5,1,1,1,1,1,2,4,1,2,1,1,1,5,1,1,2,1,3,1,4,2,3,4,4,3,1,1,3,5,3,1,1,5,2,4,1,1,3,5,1,4,3,1,1,4,2,1,1,1,1,1,1,3,1,1,1,1,1,4,5,1,2,5,3,1,1,3,1,1,1,1,5,1,2,5,1,1,1,1,1,1,3,5,1,3,2,1,1,1,1,1,1,1,4,5,1,1,3,1,5,1,1,1,1,3,3,1,1,1,4,4,1,1,4,1,2,1,4,4,1,1,3,4,3,5,4,1,1,4,1,3,1,1,5,5,1,2,1,2,1,2,3,1,1,3,1,1,2,1,1,3,4,3,1,1,3,3,5,1,2,1,4,1,1,2,1,3,1,1,1,1,1,1,1,4,5,5,1,1,1,4,1,1,1,2,1,2,1,3,1,3,1,1,1,1,1,1,1,5

6-2/main.go

@@ -0,0 +1,107 @@
+package main
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"strconv"
+)
+
+func main() {
+	fishies, err := readInput("input")
+	if err != nil {
+		fmt.Printf("Error reading or something\n%s", err)
+		return
+	}
+
+	fmt.Printf("Initializing fishies array...\n")
+	fish, _ := splitFishies(fishies)
+	fmt.Printf("Done!\n")
+
+	fishiesptr := &fish
+	// Run for i days
+	for i := 0; i < 256; i++ {
+		newfishies, _ := nextDay(*fishiesptr)
+		fishiesptr = &newfishies
+		amount := countFishies(*fishiesptr)
+		fmt.Printf("On day %d: there are %d fishies\n", i+1, amount)
+	}
+}
+
+func countFishies(fishies []int) int {
+	counter := 0
+	for i := 0; i < len(fishies); i++ {
+		counter += fishies[i]
+	}
+	return counter
+}
+
+// Read the fishies slice and returns the slice of new fishies
+func nextDay(fishies []int) ([]int, error) {
+	// Move fishies at 0 into buffer, move all fishies down the stack
+	// Add the 0 day fishies (from buffer) to the fishies at day 6
+	// Add the same amount of fishies from buffer to the 8 day counter
+	// Return the new splits
+
+	buffer := fishies[0]
+	for i := 0; i < len(fishies)-1; i++ {
+		fishies[i] = fishies[i+1]
+	}
+	fishies[6] += buffer
+	fishies[8] = buffer
+	return fishies, nil
+}
+
+// Returns a slice of the amount of fishies per day, ordered from 0 days to 8
+func splitFishies(fishies []int) ([]int, error) {
+	fishiesButSplit := make([]int, 9)
+	for i := 0; i < len(fishies); i++ {
+		fishiesButSplit[fishies[i]]++
+	}
+
+	return fishiesButSplit, nil
+}
+
+func readInput(inputfile string) ([]int, error) {
+	file, err := os.OpenFile(inputfile, 0, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	splitfunc := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
+		nextIndex := bytes.IndexByte(data, ',')
+		if nextIndex > 0 {
+			// Returning the next position aka taking only the stuff up to nextIndex and slicing off everything else
+			buffer := data[:nextIndex]
+			// nextIndex plus 1 because index is at the comma, we want the next number
+			return nextIndex + 1, bytes.TrimSpace(buffer), nil
+		}
+
+		// If we are at the end of the buffer, then return the entire buffer, but only if there is data
+		if atEOF {
+			if len(data) > 0 {
+				return len(data), bytes.TrimSpace(data), nil
+			}
+		}
+
+		// https://github.com/kgrz/reading-files-in-go/blob/master/comma-separated-string.go
+		// For more info
+		return 0, nil, nil
+	}
+
+	scanner := bufio.NewScanner(file)
+	scanner.Split(splitfunc)
+
+	fishies := make([]int, 0)
+	for scanner.Scan() {
+		fish, err := strconv.Atoi(scanner.Text())
+		if err != nil {
+			fmt.Printf("Error converting string to integer\n")
+			return nil, err
+		}
+		fishies = append(fishies, fish)
+	}
+	return fishies, nil
+}