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