## Which type of algorithm is harder to prove the correctness?

Which type of algorithm is harder to prove the correctness, dynamic programming, greedy, divide and conquer, or brute force? – Quora. Greedy is the hardest to prove because it is often not correct. If there is a solution brute force will find it and is always correct.

## Which method is better greedy or dynamic programming?

Greedy methods are generally faster. For example, Dijkstra’s shortest path algorithm takes O(ELogV + VLogV) time. Dynamic Programming is generally slower.

**Is greedy algorithm tough?**

Greedy algorithms have some advantages and disadvantages: It is quite easy to come up with a greedy algorithm (or even multiple greedy algorithms) for a problem. Analyzing the run time for greedy algorithms will generally be much easier than for other techniques (like Divide and conquer).

### Which is better divide and conquer or greedy algorithm?

Greedy is one of the optimization method….Greedy Vs. Divide and Conquer.

Divide and conquer | Greedy Algorithm |
---|---|

Divide and conquer algorithms mostly runs in polynomial time | Greedy algorithms also run in polynomial time but takes less time than Divide and conquer |

### How do you prove your correctness?

Proof of Correctness

- Its sequence of instructions.
- Its input values.
- its state, or rather, all previously initialized variables that can in any way change the output value.

**How do you prove the correctness of a recursive algorithm?**

To prove the correctness of a recursive algorithm we use mathematical induction. In a mathematical induction we want to prove a statement P(n) for all natural numbers n (possibly starting at an n0, but lets assume for simplicity we are proving the statement for all n≥1).

#### What are the advantages of dynamic programming method over Divide and conquer method?

Combine the solutions to the sub problems into the solution for the original problem. They call themselves recursively one or more times to deal with closely related sub problems. D&C does more work on the sub-problems and hence has more time consumption. In D&C the sub problems are independent of each other.

#### How dynamic programming differs from divide and conquer?

Divide and Conquer works by dividing the problem into sub-problems, conquer each sub-problem recursively and combine these solutions. Dynamic Programming is a technique for solving problems with overlapping subproblems.

**How can you prove the correctness of sorting algorithms?**

For any algorithm, we must prove that it always returns the desired output for all legal instances of the problem. For sorting, this means even if the input is already sorted or it contains repeated elements. Searching for counterexamples is the best way to disprove the correctness of some things.

## How can you prove the correctness of an algorithm using induction?

The proof consists of three steps: first prove that insert is correct, then prove that isort’ is correct, and finally prove that isort is correct. Each step relies on the result from the previous step. The first two steps require proofs by induction (because the functions in question are recursive).

## Is divide and conquer algorithm fast or slow?

For the Divide and conquer technique, it is not clear whether the technique is fast or slow. This is because at each level of recursion the size of gets smaller and the number of sub-problems increases. The difficult part is that for greedy algorithms you have to work much harder to understand correctness issues.

**Why is it so hard to prove a greedy algorithm is correct?**

The difficult part is that for greedy algorithms you have to work much harder to understand correctness issues. Even with the correct algorithm, it is hard to prove why it is correct. Proving that a greedy algorithm is correct is more of an art than a science. It involves a lot of creativity.

### Which problems can be solved using dynamic programming algorithm?

The following problems can be solved using Dynamic Programming algorithm Knapsack Problem, Weighted Job Scheduling, Floyd Warshall Algorithm, Dijkstra Shortest Path Algorithm, etc. In the Greedy Algorithm, the solution is built part by part. The decision to choose the next part is done on the basis that it gives the immediate benefit.

### What is the difference between greedy approach and dynamic programming?

Greedy approach works only in cases where it is supposed to work. Dynamic programming is more exhaustive way to search for the answer in the search space. Greedy approach is better than DP (dynamic programming) wrt speed of execution. Also a problem that can be solved using greedy ideally mostly has a hard or impossible DP solution.