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Python: nth Hamming number

Python Itertools: Exercise-26 with Solution

Write a Python program to find the nth Hamming number. User itertools module.

Hamming numbers are numbers of the form
H = 2i x 3j x 5k Where i, j, k ≥ 0
The sequence of Hamming numbers 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27. . . consists of all numbers of the form 2i.3j.5k where i, j and k are non-negative integers.

Sample Solution:

Python Code:

import itertools
from heapq import merge

def nth_hamming_number(n):
    def num_recur():
        last = 1
        yield last
        x, y, z = itertools.tee(num_recur(), 3)
        for n in merge((2 * i for i in x), (3 * i for i in y), (5 * i for i in z)):
            if n != last:
                yield n
                last = n
    result =  itertools.islice(num_recur(), n)
    return list(result)[-1]

print(nth_hamming_number(8))
print(nth_hamming_number(14))
print(nth_hamming_number(17))

Sample Output:

9
20
27

Python Code Editor:


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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m