diff --git a/cmd/04/main.go b/cmd/04/main.go new file mode 100644 index 0000000..ba53e3e --- /dev/null +++ b/cmd/04/main.go @@ -0,0 +1,82 @@ +package main + +import ( + "github.com/StevanFreeborn/advent-of-code-2025/internal/file" +) + +const PaperRollCharacter = "@" +const EmptyCharacter = "." + +type move struct { + NumberOfRows int + NumberOfColumns int +} + +var ( + up = move{NumberOfRows: -1, NumberOfColumns: 0} + down = move{NumberOfRows: 1, NumberOfColumns: 0} + right = move{NumberOfRows: 0, NumberOfColumns: 1} + left = move{NumberOfRows: 0, NumberOfColumns: -1} + upRight = move{NumberOfRows: -1, NumberOfColumns: 1} + upLeft = move{NumberOfRows: -1, NumberOfColumns: -1} + downRight = move{NumberOfRows: 1, NumberOfColumns: 1} + downLeft = move{NumberOfRows: 1, NumberOfColumns: -1} +) + +var moves = []move{ + up, + down, + right, + left, + upRight, + upLeft, + downRight, + downLeft, +} + +func SolvePartOne(filePath string) int { + input := file.ReadAllLines(filePath) + numberOfRows := len(input) + numberOfColumns := len(input[0]) + + total := 0 + + for row := range numberOfRows { + for column := range numberOfColumns { + value := string(input[row][column]) + + if value != PaperRollCharacter { + continue + } + + numberOfPaperRolls := 0 + + for _, move := range moves { + neighborRow := row + move.NumberOfRows + neighborColumn := column + move.NumberOfColumns + + if neighborRow > numberOfRows-1 || neighborRow < 0 { + continue + } + + if neighborColumn > numberOfColumns-1 || neighborColumn < 0 { + continue + } + + neighborValue := string(input[neighborRow][neighborColumn]) + + if neighborValue != PaperRollCharacter { + continue + } + + numberOfPaperRolls++ + } + + if numberOfPaperRolls < 4 { + total++ + } + } + } + + return total +} diff --git a/cmd/04/main_test.go b/cmd/04/main_test.go new file mode 100644 index 0000000..cb0ee68 --- /dev/null +++ b/cmd/04/main_test.go @@ -0,0 +1,27 @@ +package main_test + +import ( + "testing" + + solution "github.com/StevanFreeborn/advent-of-code-2025/cmd/04" +) + +func TestSolvePartOneWithExampleInput(t *testing.T) { + expected := 13 + + result := solution.SolvePartOne("EXAMPLE.txt") + + if result != expected { + t.Errorf("got %d but wanted %d", result, expected) + } +} + +func TestSolvePartOneWithInput(t *testing.T) { + expected := 1395 + + result := solution.SolvePartOne("INPUT.txt") + + if result != expected { + t.Errorf("got %d but wanted %d", result, expected) + } +}