Advent of Code 2021 Day 4

4a.go

package main

import (
	_ "embed"
	"fmt"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

type Board struct {
	Vals     [5][5]int
	Selected [5][5]bool
}

func (b *Board) Add(val int) bool {
	for row := 0; row < 5; row++ {
		for col := 0; col < 5; col++ {
			if b.Vals[row][col] == val {
				b.Selected[row][col] = true
			}
		}
	}

	// Check rows
	for row := 0; row < 5; row++ {
		ok := true
		for col := 0; col < 5; col++ {
			if !b.Selected[row][col] {
				ok = false
				break
			}
		}
		if ok {
			return true
		}
	}

	// Check cols
	for col := 0; col < 5; col++ {
		ok := true
		for row := 0; row < 5; row++ {
			if !b.Selected[row][col] {
				ok = false
				break
			}
		}
		if ok {
			return true
		}
	}

	return false
}

func (b *Board) SumUnmarked() int {
	sum := 0
	for row := 0; row < 5; row++ {
		for col := 0; col < 5; col++ {
			if !b.Selected[row][col] {
				sum += b.Vals[row][col]
			}
		}
	}
	return sum
}

func NewBoard() *Board {
	return &Board{
		Vals:     [5][5]int{},
		Selected: [5][5]bool{},
	}
}

func main() {
	chunks := strings.Split(input, "\n\n")
	inps := strings.Split(chunks[0], ",")

	boards := make([]*Board, len(chunks[1:]))
	for i, inp := range chunks[1:] {
		boards[i] = NewBoard()
		for row, val := range strings.Split(inp, "\n") {
			nums := strings.Fields(val)
			for col, num := range nums {
				var err error
				boards[i].Vals[row][col], err = strconv.Atoi(strings.TrimSpace(num))
				if err != nil {
					panic(err)
				}
			}
		}
	}

	// Go through guesses
	for _, inp := range inps {
		num, err := strconv.Atoi(strings.TrimSpace(inp))
		if err != nil {
			panic(err)
		}

		for _, board := range boards {
			if board.Add(num) {
				// Calculate score
				score := board.SumUnmarked()
				fmt.Println(score * num)
				return
			}
		}
	}
}

4b.go

package main

import (
	_ "embed"
	"fmt"
	"strconv"
	"strings"
)

//go:embed input.txt
var input string

type Board struct {
	Vals     [5][5]int
	Selected [5][5]bool
}

func (b *Board) Add(val int) bool {
	for row := 0; row < 5; row++ {
		for col := 0; col < 5; col++ {
			if b.Vals[row][col] == val {
				b.Selected[row][col] = true
			}
		}
	}

	// Check rows
	for row := 0; row < 5; row++ {
		ok := true
		for col := 0; col < 5; col++ {
			if !b.Selected[row][col] {
				ok = false
				break
			}
		}
		if ok {
			return true
		}
	}

	// Check cols
	for col := 0; col < 5; col++ {
		ok := true
		for row := 0; row < 5; row++ {
			if !b.Selected[row][col] {
				ok = false
				break
			}
		}
		if ok {
			return true
		}
	}

	return false
}

func (b *Board) SumUnmarked() int {
	sum := 0
	for row := 0; row < 5; row++ {
		for col := 0; col < 5; col++ {
			if !b.Selected[row][col] {
				sum += b.Vals[row][col]
			}
		}
	}
	return sum
}

func NewBoard() *Board {
	return &Board{
		Vals:     [5][5]int{},
		Selected: [5][5]bool{},
	}
}

func main() {
	chunks := strings.Split(input, "\n\n")
	inps := strings.Split(chunks[0], ",")

	boards := make([]*Board, len(chunks[1:]))
	for i, inp := range chunks[1:] {
		boards[i] = NewBoard()
		for row, val := range strings.Split(inp, "\n") {
			nums := strings.Fields(val)
			for col, num := range nums {
				var err error
				boards[i].Vals[row][col], err = strconv.Atoi(strings.TrimSpace(num))
				if err != nil {
					panic(err)
				}
			}
		}
	}

	// Go through guesses
	finished := make(map[int]bool)
	for _, inp := range inps {
		num, err := strconv.Atoi(strings.TrimSpace(inp))
		if err != nil {
			panic(err)
		}

		for i, board := range boards {
			if board.Add(num) {
				finished[i] = true
				if len(finished) == len(boards) {
					fmt.Println(num)
					score := board.SumUnmarked()
					fmt.Println(score * num)
					return
				}
			}
		}
	}
}