feat: valid sudoku

pkg/valid_sudoku/main.go

@@ -0,0 +1,46 @@
+package valid_sudoku
+
+type Multiset map[byte]bool
+
+func (m Multiset) Add(b byte) bool {
+	if b == '.' {
+		return true
+	}
+
+	exists := m[b]
+	m[b] = true
+	return !exists
+}
+
+func IsValidSudoku(board [][]byte) bool {
+	for i := range 3 {
+		for j := range 3 {
+			box := Multiset{}
+
+			for x := range 3 {
+				for y := range 3 {
+					if !box.Add(board[3*j+y][3*i+x]) {
+						return false
+					}
+				}
+			}
+		}
+	}
+
+	for i := range 9 {
+		row := Multiset{}
+		column := Multiset{}
+
+		for j := range 9 {
+			if !row.Add(board[i][j]) {
+				return false
+			}
+
+			if !column.Add(board[j][i]) {
+				return false
+			}
+		}
+	}
+
+	return true
+}