Python 2.7: Max digit sum with negative integers

Question

I'm building a program where it takes in n, the size of the array, and an array, A as input. The output should be the index of the integer with largest digit sum

I was able to get it to print correctly for positive numbers, but im having trouble including negative numbers in there as well. Any pointers would be appreciated!

i would like to keep the negative sign, so that -81 's digit sum evaluates to -7

#Calculating the maximum sum of a digit, and returns its index
def digitSum(n,A):

    new = sorted(A, key = lambda x:(sum(map(int, str(x))))) 
    ans = new[n-1]
    return A.index(ans)

#Test
D = [12,17,19,33,69,91,20]
E = [0,0,0]
F = [65346,654234,788899656,999999]
G = [-8,-9,-20,-30,-387]
print D,E,F,G
a1 = digitSum(7,D)
a2 = digitSum(3,E)
a3 = digitSum(4,F)
a4 = digitSum(5,G)
print 'index of the number with max digit sum: ', a1
print 'index of the number with max digit sum: ', a2
print 'index of the number with max digit sum: ', a3
print 'index of the number with max digit sum: ', a4

The previous 3 print just fine

[12, 17, 19, 33, 69, 91, 20] [0, 0, 0] [65346, 654234, 788899656, 999999]
index of the number with max digit sum:  4
index of the number with max digit sum:  0
index of the number with max digit sum:  2

but the last one throws an error

    new = sorted(A, key = lambda x:(sum(map(int, str(x)))))
ValueError: invalid literal for int() with base 10: '-'

Nikaido · Accepted Answer · 2019-10-07 16:41:53Z

1

So I basically created my custom str function, to handle the first negative digit:

sign = lambda x: (1, -1)[x < 0]

def my_to_str(int_):
    sign_ = sign(int_)
    int_c = abs(int_)
    str_int_c = list(str(int_c))
    if sign_ < 0:
        str_int_c[0] = "-"+str_int_c[0]
    # print(str_int_c)
    return str_int_c

def digitSum(n,A):
    new = sorted(A, key = lambda x:(sum(map(int, my_to_str(x)))))
    ans = new[n-1]
    return A.index(ans)

answered Oct 7, 2019 at 16:41

Nikaido

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Maurice Meyer · Accepted Answer · 2019-10-07 16:48:22Z

1

There is no need to convert the numbers to str, you could just pass an iterable tuple for example:

def digitSum(n,A):
    new = sorted(A, key = lambda x:(sum(map(int, (x,))))) 
    ans = new[n-1]
    return A.index(ans)

Output:

[12, 17, 19, 33, 69, 91, 20] [0, 0, 0] [65346, 654234, 788899656, 999999] [-8, -9, -20, -30, -387]

answered Oct 7, 2019 at 16:48

Maurice Meyer

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