[Introduction] What is algorithm?

1. What is Algorithm?

In computer programming terms, an algorithm is a set of well-defined instructions to solve a particular problem. It takes a set of input(s) and procedures the desired output. For example, An algorithm to add two numbers :

 

1. Take two number inputs
2. Add numbers using the + operator
3. Display the result

 

2. Qualities of a Good Algorithms

• Input and output should be defined precisely
• Each step in the algorithm should be clear and unambiguous
• Algorithms should be more effective among many different ways to solve a problem.
• An algorithm shouldn't include computer code. Instead, the algorithm should be written in such a way that it can be used in differnt programming language.

 

3. Examples of Algorithms

3.1 Add two numbers entered by the user

Step 1 : Start 
Step 2 : Declare variables num1, num2, and sum.
Step 3 : Read values num1 and num2
Step 4 : Add num1 and num2 and assign the result to sum. sum <- num1 + num2
Step 5 : Display sum
Step 6 : Stop

3.2 Find the largest number among three numbers

Step1 : Start
Step2 : Declare variables a, b and c. 
Step3 : Read variables a, b and c. 
Step4 : If a > b 
            If a > c 
                Display a is the largest number. 
            Else 
                Display c is the largest number. 
        Else 
            If b > c 
                Display b is the largest number. 
            Else 
                Display c is the largest number. 
Step5 : Stop

3.3 Find Roots of a Quardratic Equation \(ax^{2} + bx + c = 0\)

Step 1: Start
Step 2: Declare variables a, b, c, D, x1, x2, rp and ip;
Step 3: Calculate discriminant
         D ← b2-4ac
Step 4: If D ≥ 0
              r1 ← (-b+√D)/2a
              r2 ← (-b-√D)/2a 
              Display r1 and r2 as roots.
        Else     
              Calculate real part and imaginary part
              rp ← -b/2a
              ip ← √(-D)/2a
              Display rp+j(ip) and rp-j(ip) as roots
Step 5: Stop

3.4 Find the factorial of a number

Step 1: Start
Step 2: Declare variables n, factorial and i.
Step 3: Initialize variables
          factorial ← 1
          i ← 1
Step 4: Read value of n
Step 5: Repeat the steps until i = n
     5.1: factorial ← factorial*i
     5.2: i ← i+1
Step 6: Display factorial
Step 7: Stop

3.5 Check whether a number is prime or not

Step 1: Start
Step 2: Declare variables n, i, flag.
Step 3: Initialize variables
        flag ← 1
        i ← 2  
Step 4: Read n from the user.
Step 5: Repeat the steps until i=(n/2)
     5.1 If remainder of n÷i equals 0
            flag ← 0
            Go to step 6
     5.2 i ← i+1
Step 6: If flag = 0
           Display n is not prime
        else
           Display n is prime
Step 7: Stop

 

4. Source of the course

https://www.programiz.com/dsa/algorithm

What is an Algorithm?