Introduction

In this blog post, we'll share the most commonly asked coding interview questions at Dell. If you don't have months to study for your interviews, you can use AI tools like Chatmagic to generate solutions quickly and efficiently - helping you pass the interviews and get the job offer!

Problem #1: Delete Duplicate Emails

Table: Person +-------------+---------+ | Column Name | Type | +-------------+---------+ | id | int | | email | varchar | +-------------+---------+ id is the primary key (column with unique values) for this table. Each row of this table contains an email. The emails will not contain uppercase letters. Write a solution to delete all duplicate emails, keeping only one unique email with the smallest id. For SQL users, please note that you are supposed to write a DELETE statement and not a SELECT one. For Pandas users, please note that you are supposed to modify Person in place. After running your script, the answer shown is the Person table. The driver will first compile and run your piece of code and then show the Person table. The final order of the Person table does not matter. The result format is in the following example. Example 1: Input: Person table: +----+------------------+ | id | email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com | | 3 | john@example.com | +----+------------------+ Output: +----+------------------+ | id | email | +----+------------------+ | 1 | john@example.com | | 2 | bob@example.com | +----+------------------+ Explanation: john@example.com is repeated two times. We keep the row with the smallest Id = 1.

Topics: Database

Problem #2: Longest Substring Without Repeating Characters

Given a string s, find the length of the longest substring without duplicate characters. Example 1: Input: s = "abcabcbb" Output: 3 Explanation: The answer is "abc", with the length of 3. Example 2: Input: s = "bbbbb" Output: 1 Explanation: The answer is "b", with the length of 1. Example 3: Input: s = "pwwkew" Output: 3 Explanation: The answer is "wke", with the length of 3. Notice that the answer must be a substring, "pwke" is a subsequence and not a substring. Constraints: 0 <= s.length <= 5 * 104 s consists of English letters, digits, symbols and spaces.

Topics: Hash Table, String, Sliding Window