Big update: Adding all advent of codes to same repo

AdventOfCode2021/day6/day6.go

@@ -0,0 +1,69 @@
+package day6
+
+import (
+	"strconv"
+	"strings"
+)
+
+func Run(dat []byte) (int, int) {
+
+	stringDat := string(dat)
+
+	fish := strings.Split(stringDat, ",")
+
+	/**
+	 * We do not need to keep track of every fish,
+	 * We only need to keep track of the number of fish at a certain age.
+	 * Which is much more efficient than an exponentially increasing array.
+	 */
+	fishMap := make(map[int]int)
+
+	part2FishMap := make(map[int]int)
+
+	for _, value := range fish {
+		age, _ := strconv.Atoi(value)
+		fishMap[age] = fishMap[age]  + 1
+		part2FishMap[age] = part2FishMap[age] + 1
+	}
+
+	for day := 1; day <= 80; day++ {
+
+		readyFish := fishMap[0]
+
+		for i := 1; i <= 8; i++ {
+			fishMap[i - 1] = fishMap[i]
+		}
+
+		fishMap[6] = fishMap[6] + readyFish
+		fishMap[8] = readyFish
+
+	}
+
+	var part1 int = 0
+	for _, num := range fishMap {
+		part1 += num
+	}
+
+	//-------------------
+
+	for day := 1; day <= 256; day++ {
+
+		readyFish := part2FishMap[0]
+
+		for i := 1; i <= 8; i++ {
+			part2FishMap[i - 1] = part2FishMap[i]
+		}
+
+		part2FishMap[6] = part2FishMap[6] + readyFish
+		part2FishMap[8] = readyFish
+
+	}
+
+	var part2 int = 0
+	for _, num := range part2FishMap {
+		part2 += num
+	}
+
+	return part1, part2
+
+}