Problem

Given a 2D array of integers, write a function that returns true if the array is a valid Sudoku puzzle, and false otherwise.
A valid Sudoku puzzle is one in which each row, column, and 3x3 sub-array contains all of the integers from 1 to 9 with no repeats.
Example input:
[[5,3,4,6,7,8,9,1,2],
 [6,7,2,1,9,5,3,4,8],
 [1,9,8,3,4,2,5,6,7],
 [8,5,9,7,6,1,4,2,3],
 [4,2,6,8,5,3,7,9,1],
 [7,1,3,9,2,4,8,5,6],
 [9,6,1,5,3,7,2,8,4],
 [2,8,7,4,1,9,6,3,5],
 [3,4,5,2,8,6,1,7,9]]
Example output : true

Solution

def is_valid_sudoku(puzzle):
    # check rows
    for row in puzzle:
        if not is_valid_row(row):
            return False

    # check columns
    for i in range(len(puzzle)):
        column = [row[i] for row in puzzle]
        if not is_valid_row(column):
            return False

    # check 3x3 sub-arrays
    for i in range(0, len(puzzle), 3):
        for j in range(0, len(puzzle), 3):
            sub_array = [puzzle[i][j], puzzle[i][j+1], puzzle[i][j+2],
                         puzzle[i+1][j], puzzle[i+1][j+1], puzzle[i+1][j+2],
                         puzzle[i+2][j], puzzle[i+2][j+1], puzzle[i+2][j+2]]
            if not is_valid_row(sub_array):
                return False

    return True

def is_valid_row( row):
    return sorted(row) == [1, 2, 3, 4, 5, 6, 7, 8, 9]

puzzle = [[5,3,4,6,7,8,9,1,2],
          [6,7,2,1,9,5,3,4,8],
          [1,9,8,3,4,2,5,6,7],
          [8,5,9,7,6,1,4,2,3],
          [4,2,6,8,5,3,7,9,1],
          [7,1,3,9,2,4,8,5,6],
          [9,6,1,5,3,7,2,8,4],
          [2,8,7,4,1,9,6,3,5],
          [3,4,5,2,8,6,1,7,9]]

print(is_valid_sudoku(puzzle))