Hackerrank Algorithms 3

Question 1

What is the output of `list(map(lambda x: x**2, [1, 2, 3, 4]))`?

Accepted Answer

[1, 4, 9, 16]

Answer

`map` applies the lambda squaring function to each element, producing [1, 4, 9, 16].

Question 2

Which traversal of a binary tree visits nodes in the order: left subtree, root, right subtree?

Accepted Answer

In-order

Answer

In-order traversal follows left → root → right, which visits BST nodes in sorted order.

Question 3

What Python built-in can find the greatest common divisor of two integers?

Accepted Answer

math.gcd(a, b)

Answer

`math.gcd(a, b)` computes the greatest common divisor using the Euclidean algorithm.

Question 4

A sliding window of size k moves across an array of size n. What is the total number of windows?

Accepted Answer

n - k + 1

Answer

The first window starts at index 0 and the last at index n-k, giving n-k+1 total windows.

Question 5

What does `heapq.nlargest(3, [5, 1, 8, 3, 9, 2])` return?

Accepted Answer

[9, 8, 5]

Answer

`heapq.nlargest(k, iterable)` returns the k largest elements in descending order.

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