Hackerrank Python Data Structures & Algorithms 4

Question 1

What does `heapq.heappush(h, item)` guarantee about the resulting list `h`?

Accepted Answer

h[0] is always the smallest element

Answer

Python's heapq maintains a min-heap invariant, so h[0] is always the minimum element.

Question 2

What is the output of `list(zip([1,2,3], [4,5]))`?

Accepted Answer

[(1,4),(2,5)]

Answer

zip stops at the shortest iterable, so the result only contains pairs up to index 1.

Question 3

Which approach correctly implements a graph as an adjacency list in Python?

Accepted Answer

graph = {0: [1,2], 1: [0,2]}

Answer

A dict mapping each node to a list of its neighbors is the standard adjacency list representation.

Question 4

What is the average time complexity of `item in my_set` for a Python set?

Accepted Answer

O(1)

Answer

Python sets use hash tables, so membership testing is O(1) on average.

Question 5

Which code snippet correctly performs a binary search on a sorted list `arr` for target `t`?

Accepted Answer

import bisect; bisect.bisect_left(arr, t)

Answer

bisect.bisect_left returns the insertion point for t in O(log n); arr.index() is O(n).

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