Akuna Capital Software Engineer Interview Experience — Hexadecimal AND and Binary Tree Recursion

This technical interview mainly covered C++ fundamentals, bitwise operations, binary-tree recursion, and dynamic memory management. The questions themselves were not difficult, but there was a strong focus on pointer use, boundary conditions, and low-level implementation details.

1. Bitwise Operation

Question: Calculate:

0x23 & 0x34

Convert both hexadecimal values to binary:

0x23 = 0010 0011
0x34 = 0011 0100

After applying the bitwise AND:

0010 0000 = 0x20

Therefore, the result is:

0x20

The concepts tested included binary conversion, bitwise operations, and low-level fundamentals. An AND operation keeps a bit as 1 only when both corresponding bits are 1.

2. Binary Tree Fundamentals

Question: Implement a function that returns the maximum value in a binary tree.

A straightforward approach is to use DFS recursion to traverse the entire tree. On each recursive call, handle the empty-node case first. If the current node is empty, return a minimum value that will not affect the result, such as:

INT_MIN

This ensures that the correct answer is still found even if every node in the tree is negative. Then recursively calculate the maximum value in the left and right subtrees, and finally return the maximum among the current node's value, the left-subtree maximum, and the right-subtree maximum.

Common mistakes on this problem included writing the TreeNode or struct type incorrectly, traversing only one subtree, forgetting to handle a null pointer, and omitting a return value from the recursive function.