Unlock the Top 20 Coding Questions to Pass Oracle Interview

Are you one of those candidates wondering how to tackle Oracle's challenging interviews?

Do you find yourself confused about which coding problems to focus on?

Oracle is a place where you can build a rewarding career. But getting through the interview process can be tough. Many candidates feel overwhelmed by the complexity of the questions and unsure of how to prepare effectively.

Therefore, we have designed this blog to be your ultimate guide, providing you with the top 20 coding questions that will help you pass your Oracle interview.

Let's jump right in and get you one step closer to landing that attractive job at Oracle!

Section 1: Understanding Oracle’s Interview Process

Oracle was founded in 1977 by Larry Ellison, Bob Miner, and Ed Oates.

They started with a project to build a relational database management system, which they named Oracle. Their software became popular because it allowed businesses to manage large amounts of data easily and efficiently.

Over the years, Oracle has grown to become one of the largest software companies in the world, offering a wide range of products including databases, cloud solutions, and enterprise software.

Oracle Interview Format

The interview process at Oracle typically follows these steps:

• Phone Screening: This initial step involves a call with a recruiter who will ask about your background, skills, and experience. They will also provide details about the role and assess if you're a good fit.

• Online Assessment: If you pass the phone screening, you might be given an online assessment. This test can include coding challenges, technical questions, or case studies relevant to the job you’re applying for.

• Technical Interviews: This stage includes multiple rounds of technical interviews, either on-site or virtual. You’ll face coding problems, system design questions, and other technical challenges to test your skills.

• HR Interview: The final stage is an interview with a human resources representative. This focuses on behavioral questions, your career goals, and ensuring you align with Oracle's company values and culture. The entire interview process can take from three weeks to two months.

Discover the ultimate guide to crack the FAANG interview.

What Oracle Looks For

Oracle seeks candidates who demonstrate the following qualities:

• Technical Skills: A strong understanding of data structures, algorithms, and system design is essential.

• Problem-Solving Abilities: The ability to approach and solve complex problems efficiently.

• Communication Skills: Clearly explaining your thought process and solutions.

• Cultural Fit: Showing that you can work well in teams and align with Oracle’s values and work culture.

Build these 6 soft skills to clear your technical interview.

Types of Questions at Oracle Interview

Oracle interviews typically feature two main types of questions: technical and behavioral.

1. Technical Questions:

   • Data Structures and Algorithms: Expect questions on arrays, strings, trees, graphs, and sorting algorithms. For instance, you might be asked to differentiate between varchar and varchar2, or to describe the components of an Oracle database.

   • System Design: These questions evaluate your ability to design scalable systems. For example, you might be asked to design a database schema for a large application.

   • SQL and Database Management: Questions on writing SQL queries and managing databases, such as explaining aggregate functions in Oracle or the use of the ANALYZE command.

2. Behavioral Questions:

   • Teamwork and Collaboration: Examples include "Describe a time you worked with a difficult team member" or "How do you handle conflicts in a team?"

   • Career Goals and Motivation: Questions like "Why do you want to work at Oracle?" and "What are your long-term career goals?"

Avoid these top 5 common interview mistakes.

Section 2: 20 Coding Problems To Pass Oracle Interview

Here are the 20 coding problems that you need to practice for your Oracle interview:

1. Count Number of Pairs With Absolute Difference K

Problem Statement: Given an array of integers nums and a positive integer k, return the number of pairs (i, j) where i < j and the absolute difference of nums[i] and nums[j] should be equal to k. In other words, |nums[i] - nums[j]| == k.

Example:

• Input: nums = [1, 3, 5, 7], K = 2
• Expected Output: 3
• Justification: The pairs with an absolute difference of 2 are (1, 3), (3, 5), and (5, 7).

Difficulty Level: Easy

Solution: Count Number of Pairs with Absolute Difference K

2. Degree of an Array

Problem Statement: You are given an array nums containing positive integers. The degree of nums is defined as the maximum frequency of any one of its elements.

Return the minimum length of a contiguous subarray of nums, that has the same degree as nums.

Example:

• Input: nums = [1, 4, 2, 3, 2]
• Expected Output: 3
• Justification: The array's degree is 2 as it appears twice. The shortest subarray with a degree of 2 is [2, 3, 2], which has a length of 3.

Difficulty Level: Easy

Solution: Degree of an Array

3. Find Subsequence of Length K With the Largest Sum

Problem Statement: Given an integer array nums and a positive integer k, return any subsequence of nums of length k, which has the largest sum.

A subsequence maintains the original order of array elements but may exclude some, without reordering the remaining ones.

Example:

• Input: nums = [5, -2, 3, 8], k = 2
• Expected Output: [5,8]
• Justification: The subsequence [5, 8] gives the largest sum of 13, which is the maximum sum we can obtain from any subsequence of length 2.

Difficulty Level: Easy

Solution: Find Subsequence of Length K With the Largest Sum

4. Rectangle Overlap

Problem Statement: You are given a rectangle as a list [x1, y1, x2, y2], where (x1, y1) is the coordinate of its bottom-left corner, and (x2, y2) is the coordinate of its top-right corner.

The top and bottom edges of the rectangle are parallel to the X-axis, and the left and right edges are parallel to the Y-axis.

Two rectangles overlap if the rectangles share a part of the area; mere touching at edges or corners doesn't count.

Given two rectangles rec1 and rec2, return true if they overlap, otherwise return false.

Example:

• Input: rec1 = [0, 0, 1, 1], rec2 = [1, 1, 2, 2]
• Expected Output: false
• Justification: The two rectangles touch at a corner but do not share any area, thus they do not overlap.

Difficulty Level: Easy

Solution: Rectangle Overlap

5. Remove All Adjacent Duplicates In String

Problem Statement: Given a string S, remove all adjacent duplicate characters recursively to generate the resultant string.

Example:

• Input: s = "abccba"
• Expected Output: “”
• Justification: First, we remove "cc" to get "abba". Then, we remove "bb" to get "aa". Finally, we remove "aa" to get an empty string.

Difficulty Level: Easy

Solution: Remove All Adjacent Duplicates In String

6. Climbing Stairs

Problem Statement: Given a stair with 'n' steps, implement a method to count how many possible ways are there to reach the top of the staircase, given that, at every step you can either take 1 step, 2 steps, or 3 steps.

Example:

• Number of stairs (n): 3
• Number of ways = 4
• Explanation: Following are the four ways we can climb : {1,1,1}, {1,2}, {2,1}, {3}

Difficulty Level: Easy

Solution: Climbing Stairs

7. Excel Sheet Column Title

Problem Statement: Given a positive integer n, return the string referring to the corresponding column title in the Excel sheet.

Excel titles are composed of uppercase letters, where "A" denotes the first column, "B" the second, up to "Z" for the 26th column.

After "Z", the titles continue with two-letter combinations starting with "AA", "AB", and so on.

Example:

• Input: 700
• Expected Output: “ZX”
• Justification: The number 700 corresponds to the column title "ZX" in Excel, where "Z" is the 26th letter, and "X" follows in the sequence, indicating 26*26 + 24.

Difficulty Level: Easy

Solution: Excel Sheet Column Title

8. Single Element in a Sorted Array

Problem Statement: Given a sorted integer array nums in which each element appears exactly twice, and only 1 element appears exactly once, return the single element that appears only once.

Note: You must solve the problem in O(log n) time and O(1) space.

Example:

• Input: nums = [4,4,6,6,10,11,11]
• Expected Output: 10
• Justification: Here, 10 is the only number that doesn't have a pair.

Difficulty Level: Medium

Solution: Single Element in a Sorted Array

9. Pairs of Songs With Total Durations Divisible by 60

Problem Statement: You are given a list of positive integer times, where times[i] represents the duration of ith song in seconds.

Return the number of unique song pairs for which their total duration in seconds is multiple of 60. In other words, find the number of indices i, j such that i < j with (times[i] + times[j]) % 60 == 0.

Example:

• Input: times = [30, 20, 150, 100, 40, 110]
• Expected Output: 3
• Justification: The pairs of songs that can form a total duration divisible by 60 are (30, 150), (20, 100), and (20, 40). Each of these pairs sums up to a multiple of 60, hence the expected output is 3.

Difficulty Level: Medium

Solution: Pairs of Songs With Total Durations Divisible by 60

10. Asteroid Collision

Problem Statement: You are given an integer array asteroids of size n, where asteroids[i] represents the size and direction of the ith asteroid.

The size of an asteroid is represented by the absolute value of asteroids[i], and its direction is indicated by the integer's sign: positive for rightward and negative for leftward. Each asteroid moves at the same speed.

When two asteroids collide, the smaller one shatters. If they are of equal size, both are destroyed. Asteroids moving in the same direction never collide.

Return the final state of asteroids after all possible collisions have been resolved.

Example:

• Input: asteroids = [8, -3, 4, -5]
• Expected Output: [8]
• Justification: The asteroid 4 collides with -5, and since -5 is larger, 4 is destroyed. Next, -3 and -5 get destroyed when they collide with 8.

Difficulty Level: Medium

Solution: Asteroid Collision

11. Sort Colors

Problem Statement: Given an array containing 0s, 1s and 2s, sort the array in-place. You should treat numbers of the array as objects, hence, we can’t count 0s, 1s, and 2s to recreate the array.

The flag of the Netherlands consists of three colors: red, white and blue; and since our input array also consists of three different numbers that is why it is called Dutch National Flag problem.

Example:

• Input: [1, 0, 2, 1, 0]
• Expected Output: [0 0 1 1 2]

Difficulty Level: Medium

Solution: Sort Colors

12. Binary Tree Zigzag Level Order Traversal

Problem Statement: Given a binary tree, populate an array to represent its zigzag level order traversal.

You should populate the values of all nodes of the first level from left to right, then right to left for the next level and keep alternating in the same manner for the following levels.

Example:

Difficulty Level: Medium

Solution: Binary Tree Zigzag Level Order Traversal

13. Meeting Rooms II

Problem Statement: Given a list of time intervals during which meetings are scheduled, determine the minimum number of meeting rooms that are required to ensure that none of the meetings overlap in time.

Example:

• Input: [[10, 15], [20, 25], [30, 35]]
• Expected Output: 1
• Justification: There are no overlapping intervals in the given list. So, only 1 meeting room is enough for all the meetings.

Difficulty Level: Medium

Solution: Meeting Rooms II

14. 3Sum

Problem Statement: Given an array of unsorted numbers, find all unique triplets in it that add up to zero.

Example:

• Input: [-3, 0, 1, 2, -1, 1, -2]
• Expected Output: [[-3, 1, 2], [-2, 0, 2], [-2, 1, 1], [-1, 0, 1]]
• Justification: There are four unique triplets whose sum is equal to zero. smallest sum.

Difficulty Level: Medium

Solution: 3Sum

15. Simplify Path

Problem Statement: Given an absolute file path in a Unix-style file system, simplify it by converting ".." to the previous directory and removing any "." or multiple slashes. The resulting string should represent the shortest absolute path.

Example:

• Input: "/a//b////c/d//././/.."
• Expected Output: "/a/b/c"

Difficulty Level: Medium

Solution: Simplify Path

16. Integer to English Words

Problem Statement: Given a positive integer num, return the English word representation of num.

Example:

• Input: num=12345
• Expected Output: "Twelve Thousand Three Hundred Forty Five"
• Justification: The number 12345 is broken down into "Twelve Thousand" for the first two digits, followed by "Three Hundred" for the next digit, and "Forty Five" for the last two digits.

Difficulty Level: Hard

Solution: Integer to English Words

17. First Missing Positive

Problem Statement: Given an unsorted array nums containing positive and negative integers, return the smallest missing positive integer value.

Note: You must implement algorithm in O(log n) time and uses O(1) space.

Example:

• Input: [5, 3, -1, 8, 4, 2]
• Expected Output: 7
• Justification: The first missing positive integer in the array is 1.

Difficulty Level: Hard

Solution: First Missing Positive

18. Max Points on a Line

Problem Statement: Given an array containing points where points[i] = [xi, yi] represents a point on the X-Y plane, return the maximum number of points that are on the same straight line.

Example:

• Input: points = [[1,2], [3,6], [5,10], [7,14]]
• Expected Output: 4
• Justification: All points lie on the line (y = 2x), forming a straight line with all given points.

Difficulty Level: Hard

Solution: Max Points on a Line

19. Sudoku Solver

Problem Statement: Write a program to solve a Sudoku puzzle by filling the empty cells.

A sudoku solution must satisfy all of the following rules:

• Each of the digits 1-9 must occur exactly once in each row.
• Each of the digits 1-9 must occur exactly once in each column.
• Each of the digits 1-9 must occur exactly once in each of the 9 3x3 sub-boxes of the grid. The '.' character indicates empty cells.

Example:

• Input:

• Expected Output:

• Justification: The given output is the only valid Sudoku solution.

Difficulty Level: Hard

Solution: Sudoku Solver

20. Median of Two Sorted Arrays

Problem Statement: Given two sorted arrays, nums1 and nums2 of different sizes in the ascending order, return the median of two sorted arrays after merging them.

The median is the middle value in an ordered set, or the average of the two middle values if the set has an even number of elements.

Example:

• Input: [1, 3, 5] and [2, 4, 6]
• Expected Output: 3.5
• Justification: When merged, the array becomes [1, 2, 3, 4, 5, 6]. The median is the average of the middle two values, (3 + 4) / 2 = 3.5.

Difficulty Level: Hard

Solution: Median of Two Sorted Arrays

Check out these 8 tips to prepare for coding interview.

Wrapping Up

Oracle looks for candidates who not only have strong technical skills but also the ability to solve problems effectively and communicate clearly.

Build effective communication skills along with practicing a variety of coding problems, understanding the key concepts in data structures and algorithms, and improving your system design skills.

Make sure to review the top 20 coding questions we’ve discussed, as they cover a wide range of topics and will help you get a solid grasp of what to expect.