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Algorithms

An algorithm is the set of instructions in steps to solve a problem.

In real-life if you had to count the number of members in a room, you would count one by one until you finish counting the last member.

So we count a member and add one to the previously counted number, go to the next member, and repeat the same procedure until there are no members in the room. This is a step-wise procedure we use to count the number of members.

For a computer to solve a problem or perform a task for us, for example, a counting problem, we give it a sequence of instructions similar to the step-by-step procedure humans follow. An algorithm is a sequence of instructions given to computers to solve problems or perform tasks.

An algorithm can be written in a plain language, a pseudo-code or described by a diagram-based flowchart and it can be implemented in different computer programming langugages.

Pseudo-code

Pseudo-codes are a simplified version of computer programs and written in natural or human-readable language.

  • Pseudo-code can be read and followed by programmers to write computer programs.
  • Pseudo-code does not have specific syntax and can't be executed by a computer.
  • Pseudo-code can be implemented in a specific programming language.

For example, a pseudo-code of counting members in a room can be as follows:

set total_number_members to zero
loop while the input of member name is not empty
increment total_number_members by one
output total_number_members

Flowchart

An algorithm can be described as a pictorial representation with different symbols, shapes, arrow that describes the different process. Each shape describes a different process:

  • The process is represented graphically.
  • The process is described block by block with the arrows between blocks indicating the order of workflow.
  • The described steps are easy to follow.
  • Following the logic in diagram does not require understanding of the code.

For example, a flowchart of counting members is as follows:

                        .......
/ Start \
\......./
|
V
---------------------------------
| total_number_members = 0 |
---------------------------------
|
V
*
* *
* *
* *
* * no
------> * input name is not empty? * ------------
| * * |
| * * |
| * * |
| * * |
| * |
| | yes |
| V |
| ------------------------------------------- |
----| increment total_number_members by one | |
-------------------------------------------- |
|
--------------------------------
|
V
-------------------------------------
/ output total_number_members /
--------------------------------------
|
V
.......
/ End \
\......./

Python implementation

The above pseudo-code or flowchart can be followed to write a Python code as follows:

total_number_members = 0
while input("name? ") != "":
total_number_members += 1
print(total_number_members)

Output:

name? "Jack Lee"
name? "Mary Lo"
name?
2