Types of Complexity Classes

This article discusses the following complexity classes:

  1. P Class
  2. NP Class
  3. CoNP Class
  4. NP-hard
  5. NP-complete

P, NP, CoNP, NP hard and NP complete | Complexity Classes

In computer science, there exist some problems whose solutions are not yet found, the problems are divided into classes known as Complexity Classes. In complexity theory, a Complexity Class is a set of problems with related complexity. These classes help scientists to group problems based on how much time and space they require to solve problems and verify the solutions. It is the branch of the theory of computation that deals with the resources required to solve a problem. 

The common resources are time and space, meaning how much time the algorithm takes to solve a problem and the corresponding memory usage.

  • The time complexity of an algorithm is used to describe the number of steps required to solve a problem, but it can also be used to describe how long it takes to verify the answer.
  • The space complexity of an algorithm describes how much memory is required for the algorithm to operate.

Complexity classes are useful in organising similar types of problems.

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Types of Complexity Classes

This article discusses the following complexity classes:...

P Class

The P in the P class stands for Polynomial Time. It is the collection of decision problems(problems with a “yes” or “no” answer) that can be solved by a deterministic machine in polynomial time....

NP Class

The NP in NP class stands for Non-deterministic Polynomial Time. It is the collection of decision problems that can be solved by a non-deterministic machine in polynomial time....

Co-NP Class

Co-NP stands for the complement of NP Class. It means if the answer to a problem in Co-NP is No, then there is proof that can be checked in polynomial time....

NP-hard class

An NP-hard problem is at least as hard as the hardest problem in NP and it is a class of problems such that every problem in NP reduces to NP-hard....

NP-complete class

A problem is NP-complete if it is both NP and NP-hard. NP-complete problems are the hard problems in NP....