Python

Question 1

def is_valid_sudoku(s: str) -> bool:

Answer 1

from typing import List
    # --- 1.  Parse & sanity-check -----------------------------------------
    rows = [row.strip() for row in s.strip().split(';')]
    if len(rows) != 9:
        return False
    board: List[List[str]] = []
    for row in rows:
        cells = [c.strip() for c in row.split(',')]
        if len(cells) != 9:
            return False
        if any(c not in '123456789.' for c in cells):
           return False
        board.append(cells)
    # --- 2.  Row & column checks -------------------------------------------
    for i in range(9):
        row_vals = [v for v in board[i] if v != '.']
        if len(row_vals) != len(set(row_vals)):
            return False
        col_vals = [board[r][i] for r in range(9) if board[r][i] != '.']
        if len(col_vals) != len(set(col_vals)):
            return False
    # --- 3.  3×3 sub-grid checks -------------------------------------------
    for br in (0, 3, 6):
        for bc in (0, 3, 6):
            block = [
                board[r][c]
                for r in range(br, br + 3)
                for c in range(bc, bc + 3)
                if board[r][c] != '.'
            ]
            if len(block) != len(set(block)):
                return False
    return True