CS50 Fall 2025 - Lecture 3 - Algorithms (live, unedited)

This CS50 lecture, "Week 3," delves into the world of algorithms, focusing on sorting and searching techniques. The lecture begins with a practical demonstration of different counting algorithms to determine the number of people in the room, illustrating linear and divide-and-conquer approaches. It introduces key computer science concepts such as arrays, linear search, and binary search, using a hands-on activity involving volunteers searching for a specific bill among sorted and unsorted dollar bills. The lecture further explores the efficiency of algorithms using Big O notation, Omega, and Theta, and differentiates between upper and lower bounds. The discussion extends to data structures, including the creation of custom types using "typedef struct" in C, and concludes with an explanation of sorting algorithms like selection sort, bubble sort, and merge sort, complete with pseudocode and real-world visualizations.