What is algorithm?

Algorithm is the basic technique used to get the job done or problem solving. So we can say an algorithm is a finite list of instructions, most often used in solving problems or performing tasks.

Example of a real life algorithm (How to order pizza)

1. Search the pizza brands available at your locality
2. Choose the brand of pizza you want among available options
3. Decide the order method (via website or via call)
4. Now decide pickup or home delivery
5. Choose you pizza
6. Confirm order
7. Pay for order
8. Wait for delivery if you chose home delivery or pick up your pizza from store
9. Now  enjoy your delicious pizza

What is computer algorithm?

It is a well-defined procedure (set of unambiguous instructions) that allow computer to solve problem. Each and every task performed by computer with the help of algorithm.

Qualities of a good algorithm

1. Inputs and outputs should be defined precisely.
2. Each step in algorithm should be clear and unambiguous.
3. Algorithm should be most effective among many different ways to solve a problem.
4. An algorithm shouldn’t have computer code.

Write an algorithm to add two numbers entered by user

Few rules to design algorithm

1. Algorithm can be write using different ways like charts, imperative program, equations, sudo code
2. An algorithm takes an input and produces an output. Those must be well defined.
3. An algorithm can call other algorithm

Syntax proposal of algorithm writing

• Use generic imperative language that accepts recursive call
• Control Structures:
  • for all elements ∈ set do
  • for iterator =lowerbound to upperbound step increment do
  • while conditional do
  • do ------- while conditional
  • case element in value:
  • return value
  • break
  • continue
• instructions: standard c/c++ syntax
• function call : standard c / c++ syntax
• exceptions: when algorithm cannot safely terminate and / or respect the output specification

An example using syntax

Find greatest common divisor of two numbers

Input : integer a,b

Output: greatest common divisor of a and b

If a=0 then

return b

while b != 0 do

if a > b then

a = a−b

                else

b = b−a

return a