# Why Is TSP NP-Hard?

## Can NP-complete problems be solved?

If any NP-complete problem has a polynomial time algorithm, all problems in NP do.

The set of NP-complete problems is often denoted by NP-C or NPC.

Although a solution to an NP-complete problem can be verified “quickly”, there is no known way to find a solution quickly..

## Is traveling salesman NP-hard?

The travelling salesman problem (also called the traveling salesperson problem or TSP) asks the following question: “Given a list of cities and the distances between each pair of cities, what is the shortest possible route that visits each city exactly once and returns to the origin city?” It is an NP-hard problem in …

## What makes NP-hard difficult?

A problem is NP-hard if an algorithm for solving it can be translated into one for solving any NP-problem (nondeterministic polynomial time) problem. NP-hard therefore means “at least as hard as any NP-problem,” although it might, in fact, be harder.

## How do you prove TSP is NP-complete?

To prove TSP is NP-Complete, first we have to prove that TSP belongs to NP. In TSP, we find a tour and check that the tour contains each vertex once. Then the total cost of the edges of the tour is calculated. Finally, we check if the cost is minimum.

## How do you solve NP-hard problems?

Option One: Approximation Algorithms In some cases, you may be able to combat NP-hardness by using an approximation algorithm. For example, a canonical example of an NP-hard problem is the traveling salesman problem. In this problem, you’re given as input a complete graph representing a transportation network.

## Is Sudoku NP-hard?

The general problem of solving Sudoku puzzles on n2×n2 grids of n×n blocks is known to be NP-complete. For n=3 (classical Sudoku), however, this result is of little practical relevance: algorithms such as Dancing Links can solve puzzles in a fraction of a second because of the small size of the problem.

## What makes a problem NP-complete?

A problem is called NP (nondeterministic polynomial) if its solution can be guessed and verified in polynomial time; nondeterministic means that no particular rule is followed to make the guess. If a problem is NP and all other NP problems are polynomial-time reducible to it, the problem is NP-complete.

## Are NP-complete problems Decidable?

There are certain NP-Hard problems that also exist in NP. They are decidable, verifiable in polynomial time and are a polynomial reduction of an NP problem. These are said to be NP-Complete. Any NP-complete problem, using a polynomial-time function, can be reduced to SAT.

## Is Travel salesman a problem NP?

In fact, TSP belongs to the class of combinatorial optimization problems known as NP-complete. This means that TSP is classified as NP-hard because it has no “quick” solution and the complexity of calculating the best route will increase when you add more destinations to the problem.

## Is chess an NP problem?

Generalized chess may be NP-hard. Chess has an 8×8 board, generalized chess has an nxn board with many pieces. … There may be a “yes” answer and the certificate for NP might be a list of perfect moves for both players, but it’s intractable to check if those moves by black are actually perfect.

## Is it possible for a problem to be in both P and NP?

All problems in P can be solved with polynomial time algorithms, whereas all problems in NP – P are intractable. It is not known whether P = NP. However, many problems are known in NP with the property that if they belong to P, then it can be proved that P = NP.

## What is the difference between P and NP problems?

P = the set of problems that are solvable in polynomial time by a Deterministic Turing Machine. NP = the set of decision problems (answer is either yes or no) that are solvable in nondeterministic polynomial time i.e can be solved in polynomial time by a Nondeterministic Turing Machine[4].

## Can quantum computers solve NP-hard problems?

A quantum computer can solve any “search problem,” including many NP-hard problems, like SAT, in “checks”, where N is the size of the search space. This is with a general search algorithm called Grover’s algorithm . For example, for a SAT instance with n variables, there are possible ways to set all the variables.

## Is NP-hard harder than NP-complete?

An NP-hard problem can be beyond NP. The polynomial-time reduction from your X to any problem in NP does not necessarily have a polynomial-time inverse. If the inverse is harder, then the verification is harder. An NP-complete problem, on the other hand, is one that is NP-hard and itself in NP.

## How do you know if you have a NP-hard problem?

To prove that problem A is NP-hard, reduce a known NP-hard problem to A. In other words, to prove that your problem is hard, you need to describe an ecient algorithm to solve a dierent problem, which you already know is hard, using an hypothetical ecient algorithm for your problem as a black-box subroutine.

## What is NP-hard problem with example?

Examples. An example of an NP-hard problem is the decision subset sum problem: given a set of integers, does any non-empty subset of them add up to zero? That is a decision problem and happens to be NP-complete.

## Which of the following problems is not NP-hard?

Which of the following problems is not NP complete? Explanation: Hamiltonian circuit, bin packing, partition problems are NP complete problems. Halting problem is an undecidable problem.

## Is P equal to NP?

The statement P=NP means that if a problem takes polynomial time on a non-deterministic TM, then one can build a deterministic TM which would solve the same problem also in polynomial time.

## What are NP P NP-complete and NP-hard problems?

What are NP, P, NP-complete and NP-Hard problems? P is set of problems that can be solved by a deterministic Turing machine in Polynomial time. NP is set of decision problems that can be solved by a Non-deterministic Turing Machine in Polynomial time. … NP-complete problems are the hardest problems in NP set.

## Is traveling salesman NP-complete?

Traveling Salesman Optimization(TSP-OPT) is a NP-hard problem and Traveling Salesman Search(TSP) is NP-complete. However, TSP-OPT can be reduced to TSP since if TSP can be solved in polynomial time, then so can TSP-OPT(1).