From 73de067afc59efebe378a6d15b152d51010bcd42 Mon Sep 17 00:00:00 2001
From: Luke Else <mail@luke-else.co.uk>
Date: Tue, 21 Dec 2021 22:21:30 +0000
Subject: [PATCH] day 21a complete

Really happy with my approach in terms of data structure, looks like it should make it fairly easy to do part 2
---
 day21/21a/main.go | 144 ++++++++++++++++++++++++++++++++++++++++++++++
 day21/input       |   2 +
 day21/testInput   |   2 +
 3 files changed, 148 insertions(+)
 create mode 100644 day21/21a/main.go
 create mode 100644 day21/input
 create mode 100644 day21/testInput

diff --git a/day21/21a/main.go b/day21/21a/main.go
new file mode 100644
index 0000000..b2edd2c
--- /dev/null
+++ b/day21/21a/main.go
@@ -0,0 +1,144 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+func main() {
+	content := returnContent("../input")
+	// content := returnContent("../testInput")
+
+	//Construct Game board... in reverse :) (Just makes it easier for stringing them together)
+	positions := make(map[int]*GamePosition)
+	gameBoard := GameBoard{
+		Start: &GamePosition{
+			Position: 1,
+			Next:     nil,
+		},
+	}
+	positions[1] = gameBoard.Start
+	next := gameBoard.Start
+	var currentPosition *GamePosition
+
+	for i := 10; i > 1; i-- {
+		currentPosition = new(GamePosition)
+		currentPosition.Position = i
+		currentPosition.Next = next
+		next = currentPosition
+
+		positions[i] = currentPosition
+	}
+	gameBoard.Start.Next = currentPosition
+
+	//Add Players to the game
+	players := make(map[int]*Player)
+	numPlayers := 0
+
+	for _, value := range *content {
+		newPlayer := Player{
+			PlayerNum: value[0],
+			Score:     0,
+			Position:  positions[value[1]],
+		}
+		players[newPlayer.PlayerNum] = &newPlayer
+		numPlayers++
+	}
+
+	//Play the GAMEEEEEE
+	diceVal := 1
+	numRolls := 0
+	winner := 0
+
+	for {
+		for i := 1; i <= numPlayers; i++ {
+			p := players[i]
+			if p.Roll(&diceVal, &numRolls) {
+				winner = p.PlayerNum
+				break
+			}
+		}
+
+		if winner > 0 {
+			break
+		}
+	}
+
+	loser := 1
+	if winner == 1 {
+		loser = 2
+	}
+
+	fmt.Println(numRolls * players[loser].Score)
+
+}
+
+type GameBoard struct {
+	Start *GamePosition
+}
+
+type GamePosition struct {
+	Position int
+	Next     *GamePosition
+}
+
+type Player struct {
+	PlayerNum int
+	Score     int
+	Position  *GamePosition
+}
+
+func (p *Player) Roll(diceVal *int, numRolls *int) bool {
+	//simulate 3 consecutive dice rolls
+	dice := (*diceVal + 1) * 3
+	*diceVal += 3
+	*numRolls += 3
+
+	//calculate where the position will be after n positions being moved
+	position := p.Position
+	for i := 0; i < dice; i++ {
+		position = position.Next
+	}
+
+	p.Position = position
+
+	p.Score += p.Position.Position
+
+	//Return bool for if player has won
+	return p.Score >= 1000
+
+}
+
+func returnContent(path string) *[][]int {
+	//read file and return it as an array of integers
+
+	file, err := os.Open(path)
+	var content [][]int
+
+	if err != nil {
+		fmt.Println("Unlucky, the file didn't open")
+		return &content
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+
+	regex, _ := regexp.Compile(`[0-9]+`)
+
+	for scanner.Scan() {
+
+		line := regex.FindAllString(scanner.Text(), 2)
+		nums := []int{}
+
+		for i := 0; i < len(line); i++ {
+			num, _ := strconv.Atoi(line[i])
+			nums = append(nums, num)
+		}
+		content = append(content, nums)
+	}
+
+	return &content
+}
diff --git a/day21/input b/day21/input
new file mode 100644
index 0000000..ae8c076
--- /dev/null
+++ b/day21/input
@@ -0,0 +1,2 @@
+Player 1 starting position: 2
+Player 2 starting position: 7
\ No newline at end of file
diff --git a/day21/testInput b/day21/testInput
new file mode 100644
index 0000000..6dec3f4
--- /dev/null
+++ b/day21/testInput
@@ -0,0 +1,2 @@
+Player 1 starting position: 4
+Player 2 starting position: 8
\ No newline at end of file