cs61a home work1

def k_in_num(k, num):
    """
    Complete k_in_num, a function which returns True if num has the digit k and
    returns False if num does not have the digit k. 0 is considered to have no
    digits.

    >>> k_in_num(3, 123) # .Case 1
    True
    >>> k_in_num(2, 123) # .Case 2
    True
    >>> k_in_num(5, 123) # .Case 3
    False
    >>> k_in_num(0, 0) # .Case 4
    False
    """
    "*** YOUR CODE HERE ***"
    while num > 0:
        if num % k == 0:
            return True
        else:
            num = num // 10
    return False


from operator import add, sub


def a_plus_abs_b(a, b):
    """Return a+abs(b), but without calling abs.

    >>> a_plus_abs_b(2, 3)
    5
    >>> a_plus_abs_b(2, -3)
    5
    >>> a_plus_abs_b(-1, 4)
    3
    >>> a_plus_abs_b(-1, -4)
    3
    """
    if b < 0:
        f = sub
    else:
        f =  add
    return f(a, b)


def a_plus_abs_b_syntax_check():
    """Check that you didn't change the return statement of a_plus_abs_b.

    >>> # You aren't expected to understand the code of this test.
    >>> import inspect, re
    >>> re.findall(r'^\s*(return .*)', inspect.getsource(a_plus_abs_b), re.M)
    ['return f(a, b)']
    """
    # You don't need to edit this function. It's just here to check your work.


def two_of_three(i, j, k):
    """Return m*m + n*n, where m and n are the two smallest members of the
    positive numbers i, j, and k.

    >>> two_of_three(1, 2, 3)
    5
    >>> two_of_three(5, 3, 1)
    10
    >>> two_of_three(10, 2, 8)
    68
    >>> two_of_three(5, 5, 5)
    50
    """
    return min(i*i+j*j,k*k+j*j,i*i+k*k)


def two_of_three_syntax_check():
    """Check that your two_of_three code consists of nothing but a return statement.

    >>> # You aren't expected to understand the code of this test.
    >>> import inspect, ast
    >>> [type(x).__name__ for x in ast.parse(inspect.getsource(two_of_three)).body[0].body]
    ['Expr', 'Return']
    """
    # You don't need to edit this function. It's just here to check your work.


def largest_factor(n):
    """Return the largest factor of n that is smaller than n.

    >>> largest_factor(15) # factors are 1, 3, 5
    5
    >>> largest_factor(80) # factors are 1, 2, 4, 5, 8, 10, 16, 20, 40
    40
    >>> largest_factor(13) # factor is 1 since 13 is prime
    1
    """
    "*** YOUR CODE HERE ***"
    "*** YOUR CODE HERE ***"
    factor_list = []
    for i in range(2,n):
        #print(i)
        if n % i == 0:
            factor_list.append(i)
            #print(factor_list)

    if len(factor_list) > 0:
        return max(factor_list)
    else:
        return 1
        
====官方答案，比我写的优雅简单====
def largest_factor(n):
    """Return the largest factor of n that is smaller than n.

    >>> largest_factor(15) # factors are 1, 3, 5
    5
    >>> largest_factor(80) # factors are 1, 2, 4, 5, 8, 10, 16, 20, 40
    40
    >>> largest_factor(13) # factor is 1 since 13 is prime
    1
    """
    factor = n - 1
    while factor > 0:
        if n % factor == 0:
            return factor
        factor -= 1