HackerRank Python Solution - Itertools Topic - Compress the String!

• In this task, we would like for you to appreciate the usefulness of the groupby() function of itertools.

• You are given a string S. Suppose a character 'c' occurs consecutively X times in the string. Replace these consecutive occurrences of the character 'c' with (X,c) in the string.

• For a better understanding of the problem, check the explanation.

Input Format:

A single line of input consisting of the string S.

HackerRank Python Solution - Itertools Topic - itertools.combinations_with_replacement()

itertools.combinations_with_replacement(iterable, r):

• This tool returns r length subsequences of elements from the input iterable allowing individual elements to be repeated more than once.

• Combinations are emitted in lexicographic sorted order. So, if the input iterable is sorted, the combination tuples will be produced in sorted order.

Sample Code:

>>> from itertools import combinations_with_replacement
>>> 
>>> print list(combinations_with_replacement('12345',2))
[('1', '1'), ('1', '2'), ('1', '3'), ('1', '4'), ('1', '5'), ('2', '2'), ('2', '3'), ('2', '4'), ('2', '5'), ('3', '3'), ('3', '4'), ('3', '5'), ('4', '4'), ('4', '5'), ('5', '5')]
>>> 
>>> A = [1,1,3,3,3]
>>> print list(combinations(A,2))
[(1, 1), (1, 3), (1, 3), (1, 3), (1, 3), (1, 3), (1, 3), (3, 3), (3, 3), (3, 3)]

HackerRank Python Solution - Itertools Topic - itertools.combinations()

itertools.combinations(iterable, r):

• This tool returns the length subsequences of elements from the input iterable.

• Combinations are emitted in lexicographic sorted order. So, if the input iterable is sorted, the combination tuples will be produced in sorted order.

Sample Code:

>>> from itertools import combinations
>>> 
>>> print list(combinations('12345',2))
[('1', '2'), ('1', '3'), ('1', '4'), ('1', '5'), ('2', '3'), ('2', '4'), ('2', '5'), ('3', '4'), ('3', '5'), ('4', '5')]
>>> 
>>> A = [1,1,3,3,3]
>>> print list(combinations(A,4))
[(1, 1, 3, 3), (1, 1, 3, 3), (1, 1, 3, 3), (1, 3, 3, 3), (1, 3, 3, 3)]

HackerRank Python Solution - Itertools Topic - itertools.permutations()

itertools.permutations(iterable[, r]):

• This tool returns successive length permutations of elements in an iterable.

• If r is not specified or is None, then r defaults to the length of the iterable, and all possible full-length permutations are generated.

• Permutations are printed in a lexicographic sorted order. So, if the input iterable is sorted, the permutation tuples will be produced in sorted order.

Sample Code:

>>> from itertools import permutations
>>> print permutations(['1','2','3'])
<itertools.permutations object at 0x02A45210>
>>> 
>>> print list(permutations(['1','2','3']))
[('1', '2', '3'), ('1', '3', '2'), ('2', '1', '3'), ('2', '3', '1'), ('3', '1', '2'), ('3', '2', '1')]
>>> 
>>> print list(permutations(['1','2','3'],2))
[('1', '2'), ('1', '3'), ('2', '1'), ('2', '3'), ('3', '1'), ('3', '2')]
>>>
>>> print list(permutations('abc',3))
[('a', 'b', 'c'), ('a', 'c', 'b'), ('b', 'a', 'c'), ('b', 'c', 'a'), ('c', 'a', 'b'), ('c', 'b', 'a')]

HackerRank Python Solution - Itertools Topic - itertools.product()

itertools.product():

• This tool computes the cartesian product of input iterables.

• It is equivalent to nested for-loops.

• For example, product(A, B) returns the same as ((x,y) for x in A for y in B).

Sample Code:

>>> from itertools import product
>>>
>>> print list(product([1,2,3],repeat = 2))
[(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]
>>>
>>> print list(product([1,2,3],[3,4]))
[(1, 3), (1, 4), (2, 3), (2, 4), (3, 3), (3, 4)]
>>>
>>> A = [[1,2,3],[3,4,5]]
>>> print list(product(*A))
[(1, 3), (1, 4), (1, 5), (2, 3), (2, 4), (2, 5), (3, 3), (3, 4), (3, 5)]
>>>
>>> B = [[1,2,3],[3,4,5],[7,8]]
>>> print list(product(*B))
[(1, 3, 7), (1, 3, 8), (1, 4, 7), (1, 4, 8), (1, 5, 7), (1, 5, 8), (2, 3, 7), (2, 3, 8), (2, 4, 7), (2, 4, 8), (2, 5, 7), (2, 5, 8), (3, 3, 7), (3, 3, 8), (3, 4, 7), (3, 4, 8), (3, 5, 7), (3, 5, 8)]

HackerRank Python Solution - Math Topic - Triangle Quest

• You are given a positive integer N. Print a numerical triangle of height N-1 like the one below:

1
22
333
4444
55555
......

• Can you do it using only arithmetic operations, a single for loop, and print statement?

• Use no more than two lines. The first line (the for statement) is already written for you. You have to complete the print statement.

• Note: Using anything related to strings will give a score of 0.

HackerRank Python Solution - Math Topic - Integer Come In All Sizes

• Integers in Python can be as big as the bytes in your machine's memory. There is no limit in size as there is: 2³¹-1 (c++ int) or 2⁶³-1 (C++ long long int).

• As we know, the result of a^b grows really fast with increasing b.

• Let's do some calculations on very large integers.