Does an algorithm have to be correct?

An important aspect of any algorithm is that it is correct: it always produces the expected output for the range of inputs and it eventually terminates. Programmers often use empirical analysis to find faults in an algorithm, but only formal reasoning can prove total correctness.

Is it possible to create an algorithm that will solve the problem for all programs and inputs?

Some problems take a very long time to solve, so we use algorithms that give approximate solutions. An undecidable problem is one that should give a “yes” or “no” answer, but yet no algorithm exists that can answer correctly on all inputs.

What is the difference between an algorithm for solving a problem and a computer program that solves this problem?

An algorithm is a self-contained step-by-step set of operations to be performed to solve a specific problem or a class of problems. A computer program is a sequence of instructions that comply the rules of a specific programming language , written to perform a specified task with a computer.

How do you change an algorithm into a program?

From Algorithm to Code

1. Divide the smaller number into the larger one and get the remainder (i.e. 450 / 100 = 4 with a remainder of 50)
2. Repeat Step 1 with the smaller of the two numbers and the remainder (i.e. 100 / 50 = 2 with no remainder)

What does it mean for an algorithm to be correct?

An algorithm is correct only if it produces correct result for all input instances. – If the algorithm gives an incorrect answer for one or more input instances, it is an incorrect algorithm.

Is a condition that is always true at a particular point in an algorithm?

Invariant means that it checks the condition of algorithm if the condition of algorithm is true then the statement inside that block in the algorithm is executed . The invariant is a statement in the algorithm i.e it is a parameters, that is valid each time when the instruction execution hits the invariant.

What’s the difference between an algorithm and a program?

An algorithm is more like an idea, a way to solve a problem, while a program is more linked to the execution of one or more tasks by a computer. A program can implement one or more algorithms, or it may be so simple that we don´t have to use an algorithm.

What is the difference between an algorithm and a program class 11?

Algorithm – It is a well-defined, systematic logical approach that comes with a step-by-step procedure for computers to solve any given program. Program – It refers to the code (written by programmers) for any program that follows the basic rules of the concerned programming language.

Why is it so hard to reverse a password hashing algorithm?

The hash function is designed so it is hard to reverse it and get any answer at all, even a different password with the same hash. In crypto-speak: a hash function vulnerable to a preimage attack is utterly worthless. (The password hashing algorithm above is injective if you have a rule that x < y.)

How to reverse a hash to the original input?

You can not reverse them to the original input as a hash function drops too much of the input information. You’ll never know if you’ve got the correct input… and no computing power in the world can help (unless the hash function is broken/flawed, and even then only in cases where hashInputSize <= hashOutputSize).

Why do hash algorithms always contain non-linear operations?

Non-linearity: Hashing algorithms always contain non-linear operations – this prevents people from using linear algebra techniques to “solve” the input from a given output. Note the addition example I use above is a linear operation; building a hash algorithm using just addition operators is a really bad idea!

How do hashing algorithms work in real life?

In reality, hashing algorithms use many combinations of linear and non-linear operations. All of this adds up to a situation where the easiest way of finding a matching hash is just to guess a different input, hash it and see if it matches.