Find all possible prime numbers in a given range

AI Summary

An AI-generated summary of this video lecture.

This video is a programming lecture from Knowledge Gate, a channel focused on placement preparation. The instructor, Yash Jain, presents a problem (Q5) to find all prime numbers within a given range. The problem statement, input/output format, and public test cases are displayed on a slide. The instructor then writes a C program to solve the problem, using a function named findPrime to check if a number is prime. The algorithm checks divisibility up to the square root of the number for efficiency. The code is then demonstrated in an online C compiler, where it is successfully compiled and executed, producing the correct output for the test cases. The video concludes with the instructor explaining the code's logic and performance.

Chapters

1. 0:00 – 2:00 00:00-02:00

   The video begins with the Knowledge Gate logo, followed by a slide introducing the problem. The problem (Q5) is to write a program to find all prime numbers within a given range. The input is two integers (start and end), and the output is a list of prime numbers separated by spaces. Two public test cases are shown: one for the range 1 to 10, which should output 2 3 5 7, and another for 1 to 100, which should output all primes up to 97. The instructor, Yash Jain, is visible in a small window, explaining the problem. A digital timer is also visible on the slide, counting down from 4:58 to 4:00.

2. 2:00 – 3:26 02:00-03:26

   The instructor transitions to a code editor, displaying a C program. The code includes a function `int findPrime(int n)` that returns 1 if the number is prime and 0 otherwise. The function uses a flag variable and a loop that iterates from 2 to the square root of n to check for divisors. If a divisor is found, the flag is set to 0 and the loop breaks. The main function reads the start and end of the range, then iterates through each number, calling `findPrime` and printing the number if it is prime. The instructor explains the logic, with handwritten annotations on the code. The video then shows the code being compiled and run in an online C compiler, where it successfully outputs the correct list of prime numbers for the 1 to 100 test case.

The video provides a complete, step-by-step tutorial on solving a common programming interview question. It starts with a clear problem definition, then moves to a practical implementation in C. The instructor demonstrates a standard algorithm for checking primality, emphasizing the optimization of checking divisors only up to the square root of the number. The final part of the video validates the solution by running it in a real environment, reinforcing the learning by showing the correct output. This structured approach, from problem to solution to verification, is effective for teaching programming concepts.