How to resolve the algorithm Tau number step by step in the Python programming language
How to resolve the algorithm Tau number step by step in the Python programming language
Table of Contents
Problem Statement
A Tau number is a positive integer divisible by the count of its positive divisors.
Show the first 100 Tau numbers. The numbers shall be generated during run-time (i.e. the code may not contain string literals, sets/arrays of integers, or alike).
Let's start with the solution:
Step by Step solution about How to resolve the algorithm Tau number step by step in the Python programming language
The given Python code provides two approaches to finding and printing the first 100 "Tau numbers." Tau numbers are positive integers that are divisible by the count of their positive divisors.
Approach 1: Using a Loop and Assertions
The first part of the code uses a loop and assertions to find Tau numbers:
- The
tau
function takes an integern
and calculates the number of positive divisors ofn
. - The
is_tau_number
function checks ifn
is a Tau number by determining ifn
is divisible by the number of its divisors. - The code iterates through positive integers until it finds 100 Tau numbers and stores them in the
ans
list.
Approach 2: Using Generators and Functional Programming
The second part of the code utilizes generators and functional programming techniques:
- The
tauNumbers
generator yields Tau numbers indefinitely. - The
divisors
function returns a list of divisors for a given number. - The
primeFactors
function extracts the prime factors of a number. - The code uses various helper functions, such as
chunksOf
,take
, anduntil
, to manipulate and format the data.
Main Function:
The main
function uses the tauNumbers
generator to compute the first 100 Tau numbers and prints them in a formatted manner using chunksOf
to group them into columns.
Source code in the python programming language
def tau(n):
assert(isinstance(n, int) and 0 < n)
ans, i, j = 0, 1, 1
while i*i <= n:
if 0 == n%i:
ans += 1
j = n//i
if j != i:
ans += 1
i += 1
return ans
def is_tau_number(n):
assert(isinstance(n, int))
if n <= 0:
return False
return 0 == n%tau(n)
if __name__ == "__main__":
n = 1
ans = []
while len(ans) < 100:
if is_tau_number(n):
ans.append(n)
n += 1
print(ans)
'''Tau numbers'''
from operator import mul
from math import floor, sqrt
from functools import reduce
from itertools import (
accumulate, chain, count,
groupby, islice, product
)
# tauNumbers :: Generator [Int]
def tauNumbers():
'''Positive integers divisible by the
count of their positive divisors.
'''
return (
n for n in count(1)
if 0 == n % len(divisors(n))
)
# ------------------------- TEST -------------------------
# main :: IO ()
def main():
'''The first hundred Tau numbers.
'''
xs = take(100)(
tauNumbers()
)
w = len(str(xs[-1]))
print('\n'.join([
' '.join([
str(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
# divisors :: Int -> [Int]
def divisors(n):
'''The ordered divisors of n.
'''
def go(a, x):
return [a * b for a, b in product(
a,
accumulate(chain([1], x), mul)
)]
return sorted(
reduce(go, [
list(g) for _, g
in groupby(primeFactors(n))
], [1])
) if 1 < n else [1]
# primeFactors :: Int -> [Int]
def primeFactors(n):
'''A list of the prime factors of n.
'''
def f(qr):
r = qr[1]
return step(r), 1 + r
def step(x):
return 1 + (x << 2) - ((x >> 1) << 1)
def go(x):
root = floor(sqrt(x))
def p(qr):
q = qr[0]
return root < q or 0 == (x % q)
q = until(p)(f)(
(2 if 0 == x % 2 else 3, 1)
)[0]
return [x] if q > root else [q] + go(x // q)
return go(n)
# take :: Int -> [a] -> [a]
# take :: Int -> String -> String
def take(n):
'''The prefix of xs of length n,
or xs itself if n > length xs.
'''
def go(xs):
return (
xs[0:n]
if isinstance(xs, (list, tuple))
else list(islice(xs, n))
)
return go
# until :: (a -> Bool) -> (a -> a) -> a -> a
def until(p):
'''The result of repeatedly applying f until p holds.
The initial seed value is x.
'''
def go(f):
def g(x):
v = x
while not p(v):
v = f(v)
return v
return g
return go
# MAIN ---
if __name__ == '__main__':
main()
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