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  1. Forming a Magic Square
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Forming a Magic Square

  • strawmsc
     + 0 comments

    Idk why all the python answers assume you'd have access to a list of all magic squares when doing this problem.I guess to game the hackerrank rankings? Not very helpful for people actually trying to learn. Anyways, Here's how I would solve this on an actual test, including code to find all magic squares:

    def is_magic(s):
    
    # Rows
    if not all(sum(row) == 15 for row in s):
        return False

    # Columns
    for col in range(3):
        if s[0][col] + s[1][col] + s[2][col] != 15:
            return False

    # Diagonals
    if (s[0][0] + s[1][1] + s[2][2] != 15 or
        s[0][2] + s[1][1] + s[2][0] != 15):
        return False

    return True
    
    
def formingMagicSquare(s):
    magic_squares = []
    
    for perm in permutations(range(1, 10)): 
        
        square = [list(perm[0:3]), list(perm[3:6]), list(perm[6:9])]
        
        if is_magic(square):
            magic_squares.append(square)


    min_cost = math.inf
    for square in magic_squares:
        cost = 0
        for i in range(3):
            for j in range(3):
                cost+=abs(s[i][j] - square[i][j])
        
        min_cost = min(min_cost,cost)
    
    return min_cost