6-1 complete

6-1/main.go

@@ -1,7 +1,89 @@
 package main
 
-import "fmt"
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"os"
+	"strconv"
+)
 
 func main() {
-	fmt.Printf("Yeet")
+	fishies, err := readInput("input")
+	if err != nil {
+		fmt.Printf("Error reading or something\n%s", err)
+		return
+	}
+	fishiesptr := &fishies
+	// Run for i days
+	for i := 0; i < 80; i++ {
+		newfishies, _ := nextDay(*fishiesptr)
+		fishiesptr = &newfishies
+		fmt.Printf("On day %d: there are %d fishies\n", i+1, len(newfishies))
+	}
+}
+
+// Read the fishies slice and returns the slice of new fishies
+func nextDay(fishies []int) ([]int, error) {
+	// For every fish (integer) in the slice, decrement by 1 if >= 1, reset to 6 if it was 0
+	// Also, if the number was 0, add a new fish with counter 8 to a second slice
+	// After everything, append the slices and return the result
+	newfishies := make([]int, 0)
+	for i := 0; i < len(fishies); i++ {
+		if fishies[i] >= 1 {
+			fishies[i] -= 1
+			continue
+		}
+		if fishies[i] == 0 {
+			fishies[i] = 6
+			newfishies = append(newfishies, 8)
+			continue
+		}
+	}
+
+	fishies = append(fishies, newfishies...)
+	return fishies, 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
 }