## How do you prove NP hardness?

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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.

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

2.1. P and NP

- The problem belongs to class.
- Similarly, the problem belongs to class.
- Reduction of a problem to problem is a conversion of inputs of problem to the inputs of problem.
- The problem is -Hard if every problem from polynomially reduces to it.
- The problem is -Complete if it belongs to , and every problem from.

**How do you prove NP?**

We can solve Y in polynomial time: reduce it to X. Therefore, every problem in NP has a polytime algorithm and P = NP. then X is NP-complete. In other words, we can prove a new problem is NP-complete by reducing some other NP-complete problem to it.

### What is NP hardness explain?

In computational complexity theory, NP-hardness (non-deterministic polynomial-time hardness) is the defining property of a class of problems that are informally “at least as hard as the hardest problems in NP”. A simple example of an NP-hard problem is the subset sum problem.

### Can you solve NP-hard problems?

NP-Hard problems(say X) can be solved if and only if there is a NP-Complete problem(say Y) that can be reducible into X in polynomial time. NP-Complete problems can be solved by a non-deterministic Algorithm/Turing Machine in polynomial time.

**How do you reduce NP-hard?**

We can show that our new problem is NP-Hard by reducing another known NP-Hard problem to it in polynomial time….Show that the problem is NP-Hard

- Step 1 – Transform Input.
- Step 2 – Use Blackbox for Problem A.
- Step 3 – Transform Solution.
- Step 4 – Provide Proof.

#### What are the steps involved in proving a problem NP-complete?

In order to prove that a problem L is NP-complete, we need to do the following steps:

- Prove your problem L belongs to NP (that is that given a solution you can verify it in polynomial time)
- Select a known NP-complete problem L’
- Describe an algorithm f that transforms L’ into L.

#### How do you solve NP-hard problems?

NP-Hard problems(say X) can be solved if and only if there is a NP-Complete problem(say Y) that can be reducible into X in polynomial time. NP-Complete problems can be solved by a non-deterministic Algorithm/Turing Machine in polynomial time. To solve this problem, it do not have to be in NP .

**What is the difference between NP-hard and NP-complete?**

A Problem X is NP-Hard if there is an NP-Complete problem Y, such that Y is reducible to X in polynomial time….Difference between NP-Hard and NP-Complete:

NP-hard | NP-Complete |
---|---|

To solve this problem, it do not have to be in NP . | To solve this problem, it must be both NP and NP-hard problems. |

## 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 to check the hardness of a metal?

This is probably the most common way of professionally and accurately checking the hardness of metals. A rounded steel ball or conical diamond tip is pushed into the metal, and the depth of the indent is measured by the machine.

**What is the hardness of a material?**

The hardness value indicates the ability of the surface of a material to resist plastic deformation caused by the intrusion of another object. When measuring the hardness by the back-jumping method, the hardness value represents the size of the metalâ€™s elastic deformation function.

### What if the hardness value is less than 20hrc?

When the hardness value is less than 20HRC, because the conical part of the indenter is pressed too much, the sensitivity is reduced, and the HRB scale should be used instead.

### What is indentation hardness of metal?

The most common Brinell, Rockwell, and Vickers hardnesses of metal materials are all indentation hardness. The hardness value indicates the ability of the surface of a material to resist plastic deformation caused by the intrusion of another object.