Sum of the digits of n is substring of n: Difference between revisions

or as a full script, taking an alternative route, and slightly reducing the number of str conversions required:

<lang python>'''Sum of the digits of n is substring of n'''

from functools import reduce

# digitSumIsSubString :: String -> Bool

def digitSumIsSubString(s):

'''True if the sum of the decimal digits in s

matches any contiguous substring of s.

'''

return str(

reduce(lambda a, c: a + int(c), s, 0)

) in s

# ------------------------- TEST -------------------------

# main :: IO ()

def main():

'''Matches in [1..999]'''

xs = list(

filter(

digitSumIsSubString,

(str(n) for n in range(1, 1000))

)

)

w = len(xs[-1])

print(f'{len(xs)} matches < 1000:\n')

print(

'\n'.join(

' '.join(cell.rjust(w, ' ') for cell in row)

for row in chunksOf(10)(xs)

)

)

# ----------------------- GENERIC ------------------------

# chunksOf :: Int -> [a] -> [[a]]

def chunksOf(n):

'''A series of lists of length n, subdividing the

contents of xs. Where the length of xs is not evenly

divible, the final list will be shorter than n.

'''

def go(xs):

return (

xs[i:n + i] for i in range(0, len(xs), n)

) if 0 < n else None

return go

# MAIN ---

if __name__ == '__main__':

main()

</lang>

{{Out}}

<pre>47 matches < 1000:

1 2 3 4 5 6 7 8 9 10

20 30 40 50 60 70 80 90 100 109

119 129 139 149 159 169 179 189 199 200

300 400 500 600 700 800 900 910 911 912

913 914 915 916 917 918 919</pre>