Add solution for 2021 day 04

2021/README.md

@@ -7,7 +7,7 @@
 | 01  |   ✓    |   ✓    | Ruby     |
 | 02  |   ✓    |   ✓    | Ada      |
 | 03  |   ✓    |   ✓    | Perl     |
-| 04  |        |        |          |
+| 04  |   ✓    |   ✓    | Go       |
 | 05  |        |        |          |
 | 06  |        |        |          |
 | 07  |        |        |          |

2021/day-04/aoc/aoc.go

@@ -0,0 +1,119 @@
+package aoc
+
+import (
+    "os"
+    "io"
+    "errors"
+    "bufio"
+    "strings"
+    "strconv"
+)
+
+type Field struct {
+    Marked bool
+    Value int
+}
+
+type Board struct {
+    Fields [5][5]Field
+    Completed bool
+}
+
+const (
+    READ_NUMBERS = 0
+    READ_BOARD = 1
+)
+
+func strs_to_ints(num_strs []string) []int {
+    var numbers []int
+
+    for _, num_str := range num_strs {
+        i, _ := strconv.Atoi(num_str)
+        numbers = append(numbers, i)
+    }
+
+    return numbers
+}
+
+func ReadFile(path string) ([]int, []Board, error) {
+    file, err := os.Open(path)
+    defer file.Close()
+
+    if err != nil {
+        return nil, nil, err
+    }
+
+    reader := bufio.NewReader(file)
+
+    var state = READ_NUMBERS
+
+    var numbers []int
+
+    var boards []Board
+    var cur_fields [5][5]Field
+    var row_idx = 0
+
+    reader:for {
+        line, err := reader.ReadString('\n')
+        var end_of_file = errors.Is(err, io.EOF)
+        if err != nil && !end_of_file { break }
+
+        var state_change = line == "\n" || end_of_file
+        line = strings.TrimRight(line, "\n")
+
+        switch state {
+            case READ_NUMBERS:
+                if state_change {
+                    state = READ_BOARD
+                    continue
+                }
+                var num_strs = strings.Split(line, ",")
+                numbers = strs_to_ints(num_strs)
+            case READ_BOARD:
+                if state_change {
+                    var board = Board{Fields: cur_fields, Completed: false}
+                    boards = append(boards, board)
+                    row_idx = 0
+                    if end_of_file { break reader }
+                    continue
+                }
+                var num_strs = strings.Fields(line)
+                for col_idx, value := range strs_to_ints(num_strs) {
+                    cur_fields[row_idx][col_idx] = Field{Value: value, Marked: false}
+                }
+                row_idx += 1
+        }
+    }
+
+    return numbers, boards, nil
+}
+
+func check_row(i int, board *Board) bool {
+    for _, field := range board.Fields[i] {
+        if !field.Marked { return false }
+    }
+    return true
+}
+
+func check_col(j int, board *Board) bool {
+    for _, row := range board.Fields {
+        if !row[j].Marked { return false }
+    }
+    return true
+}
+
+func MarkBoard(board *Board, number int) bool {
+    for i, row := range board.Fields {
+        for j, _ := range row {
+            var field = &board.Fields[i][j]
+            if field.Value == number {
+                field.Marked = true
+                if check_row(i, board) || check_col(j, board) {
+                    return true
+                }
+            }
+        }
+    }
+
+    return false
+}

2021/day-04/go.mod

@@ -0,0 +1,3 @@
+module aoc
+
+go 1.17

2021/day-04/inputs/puzzle.txt

@@ -0,0 +1,601 @@
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+
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2021/day-04/inputs/sample.txt

@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
+
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
+
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7

2021/day-04/part_one.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+    "os"
+    "fmt"
+    . "aoc/aoc"
+)
+
+func find_winner(numbers []int, boards []Board) (*Board, int) {
+    for _, number := range numbers {
+        for b, _ := range boards {
+            if MarkBoard(&boards[b], number) {
+                return &boards[b], number
+            }
+        }
+    }
+
+    return nil, -1
+}
+
+func main() {
+    path := os.Args[1]
+
+    numbers, boards, err := ReadFile(path)
+
+    if err != nil {
+        os.Exit(1)
+    }
+
+    board, last_number := find_winner(numbers, boards)
+
+    var unmarked_sum = 0
+    for _, row := range board.Fields {
+        for _, col := range row {
+            if !col.Marked {
+                unmarked_sum += col.Value;
+            }
+        }
+    }
+
+    fmt.Println(unmarked_sum * last_number)
+}

2021/day-04/part_two.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+    "os"
+    "fmt"
+    . "aoc/aoc"
+)
+
+func find_winner(numbers []int, boards []Board) (*Board, int) {
+    var boards_left = len(boards)
+    for _, number := range numbers {
+        for b, _ := range boards {
+            if boards[b].Completed { continue }
+
+            if MarkBoard(&boards[b], number) {
+                if boards_left == 1 {
+                    return &boards[b], number
+                }
+                boards[b].Completed = true
+                boards_left -= 1;
+            }
+        }
+    }
+
+    return nil, -1
+}
+
+func main() {
+    path := os.Args[1]
+
+    numbers, boards, err := ReadFile(path)
+
+    if err != nil {
+        os.Exit(1)
+    }
+
+    board, last_number := find_winner(numbers, boards)
+
+    var unmarked_sum = 0
+    for _, row := range board.Fields {
+        for _, col := range row {
+            if !col.Marked {
+                unmarked_sum += col.Value;
+            }
+        }
+    }
+
+    fmt.Println(unmarked_sum * last_number)
+}

README.md

@@ -8,4 +8,4 @@
 -   [2018](2018/README.md) (0% completed)
 -   [2019](2019/README.md) (0% completed)
 -   [2020](2020/README.md) (4% completed)
--   [2021](2021/README.md) (12% completed)
+-   [2021](2021/README.md) (16% completed)