Day 2 – Hashmaps | Hashing | Leetcode Interview Crash Course (Data Science & DSA)

This is Day 2 of my Leetcode Interview Crash Course — a fast-paced, 7-day prep series covering all the core Data Science & DSA patterns.

In this video, I cover the Hashmap / Hashing data-structure pattern and its most common interview applications — existence checking, frequency counting, and deduplication.

00:00 — Intro & Course Context
00:37 — What is Hashing?
00:40 — Data Structures as Organized Formats
00:47 — Interface vs Implementation
00:53 — How Data Structures Work Internally
01:35 — Hash Functions & Key Conversion
04:35 — Example: Simple Hash Function for Strings
09:09 — Arrays vs Hashmaps (Keys → Values Mapping)
09:40 — Hashmaps, Dictionaries & Implementation in Python
10:56 — Sets vs Hashmaps (Key Only vs Key–Value)
13:03 — Common Hashmap Operations (add, delete, update, keys, values)
14:46 — Checking for Existence (Intro to First Module)
07:20 — Example 1: Two Sum Problem
08:27 — Example 2: First Duplicate Character (Using Set)
08:58 — Example 3: Numbers Where x + 1 Missing
12:44 — Example 4: Pangram Check (All 26 Letters)
14:52 — Example 5: Missing Number (Using Set)
16:15 — Example 6: Counting Elements (x + 1 Exists)
19:41 — Wrap-Up & Next Topic Preview

Видео Day 2 – Hashmaps | Hashing | Leetcode Interview Crash Course (Data Science & DSA) канала AIwithMJ