HackerRank Questions solved in Python 3
PURPOSE
Storing Python solutions for questions that I solve on HackerRank
Return reverse of Array
Using list slicing to reverse array
def reverseArray(a):
"""reverse of input list
Parameters
----------
a: list
Returns
-------
list
"""
return a[::-1]
rev = reverseArray(['1', '2', '3'])
print(rev)Methods to reverse a list in Python
Creating 2D Arrays
In Python, there are no arrays, there's only list. To create a 2D Array, (or 2D list), we can wrap one list inside the other.
# using append
arr = []
arr.extend([[], []])
print(arr)
arr[0].append('this works as expected')
print(arr)
# using range
arr = [[] for i in range(10)]
print(arr)
arr[0].append('this works as expected')
print(arr)
# using multiplication
# BEWARE: This will create duplicate-interlined elements. Pointer Nightmare intensifies.
# reference: https://stackoverflow.com/a/8183201/7048915
arr = [[]]*10
print(arr)
arr[0].append('this will be added to all the elements, even though I am specifying index 0')
print(arr)def dynamicArray(n, queries):
"""Generate a list of answers based on input queries
if query type is 1,
- append the 3rd element of query into arr[index]
if query type is 2:
- lastAnswer = arr[idx][y % len(arr[idx])]
- calculate and append answer to answer list
Parameters
----------
n: int
number of sub arrays
queries: list
inputs of this list decides the answer
Returns
-------
list
list of answers
"""
arr = [[] for i in range(n)]
answers = []
lastAnswer = 0
for i in queries:
query_type, x, y = i
idx = ((x^lastAnswer)%n)
if query_type == 1:
arr[idx].append(y)
elif query_type == 2:
lastAnswer = arr[idx][y % len(arr[idx])]
answers.append(lastAnswer)
return answers