The sieve of Eratosthenes is an ancient algorithm for finding all prime numbers up to any given limit. It does so by iteratively marking numbers in the range as composite by marking the multiples of each prime as non-prime.

Activity selection problem is the problem of selecting the largest set of mutually exclusive activities. Each activity has its own starting time si and finish time fi. No two activities can share the resource at any time point.

There are n jobs to be processed on a machine. Each job i has a deadline and a profit. Profit is earned if the job is completed by its deadline. Job is completed if it is processed on a machine for unit time.

A message containing letters from A-Z can be encoded into numbers. To decode an encoded message, all the digits must be grouped then mapped back into letters using the reverse of the mapping

Greedy approach and Dynamic programming both are used for solving optimisation problems. However often we need to use DP since optimal solution cannot be guaranteed by a greedy algorithm.

The number of possible partition of a set of n elements is B(n) known as Bell number. As we know, this problem is NP-Complete i.e. it has non-polynomial time solution.