Oracle Senior+ Platform Engineer Interview Experience — First Technical Round

Round 1: Technical Interview

Maximum of Minimums of Every Window

Given an array A of size n and an integer x, implement the following steps:

1. Consider every contiguous subarray of length x, or sliding window.
2. Find the minimum value in each window.
3. Return the maximum of all those minimum values.

For example, A = [1, 3, -1, 5, 3, 6] and x = 3:

[1, 3, -1] -> minimum is -1
[3, -1, 5] -> minimum is -1
[-1, 5, 3] -> minimum is -1
[5, 3, 6] -> minimum is 3

The final return value is 3.

The main point of the question is to use a sliding window and a monotonic deque to maintain the current window's minimum efficiently and avoid repeated computation.

SQL — Classify Nodes in a Tree

Given a Tree table containing id (node ID) and pid (parent node ID), write a SQL query that classifies each node as follows:

1. Root: has no parent, so pid is NULL.
2. Inner: has at least one child and also has a parent.
3. Leaf: has no children and has a parent.

Example input:

id   pid
1    NULL
2    1
3    1
4    2

Expected output:

1 -> Root
2 -> Inner
3 -> Leaf
4 -> Leaf