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Algorithm


What is an algorithm?

Algorithm is a procedure or step by step process for solving a problem.

  • Algorithms can be expressed using different kinds of notations, including pseudocode, flowcharts, programming languages and natural languages.

  • Computer algorithm is an instance of logic written in computer software by the programmers.


Let’s learn some of the algorithm. Sample problem definition and algorithm is given below:

1. Problem Definition: Write an algorithm to add given two numbers.

Step 1: Start.

Step 2: Read two numbers A and B.

Step 3: Total = A+B.

Step 4: Display Total.

Step 5: Stop.


Algorithm to C program conversion

 Example of Algorithm to C program conversion.

Problem Definition: Write an algorithm to add given two numbers.

Step 1: Start.

Step 2: Read two numbers A and B.

Step 3: Total = A+B.

Step 4: Display Total.

Step 5: Stop.



#include<stdio.h>
int main()
{
 int A, B, Answer;

 printf("Enter number A:");
 scanf("%d",&A);

 printf("Enter number B:");
 scanf("%d",&B);

 Answer = A + B;
 printf("%d", Answer);
 return 0;
}

Output of program:

Enter number A:5
Enter number B:10
15

2. Problem Definition: Write an algorithm for Subtracting two Numbers.

Step 1: Start.

Step 2: Read two numbers A and B.
Step 3: Answer = A - B.
Step 4: Display SUB.
Step 5: Stop.


Example of Algorithm to C program conversion.

 Example of Algorithm to C program conversion.

Problem Definition: Write an algorithm for Subtracting two Numbers.

Step 1: Start.
Step 2: Read two numbers A and B.
Step 3: Answer = A - B.
Step 4: Display Answer.
Step 5: Stop


#include<stdio.h>
int main()
{
int A, B, Answer;

printf("Enter number A:");
scanf("%d",&A);

printf("Enter number B:");
scanf("%d",&B);

Answer = A - B;
printf("%d", Answer);
 return 0;
}

3. Problem Definition: Write an algorithm to find factorial of a given number.

Step 1: Start
Step 2: Declare variables: N, fact,  i.
Step 3: Initialize variables
            fact = 1
            i = 1
Step 4: Read value of N from user.
Step 5: Repeat following steps until i = N
            fact =  fact * i
            i = i + 1
Step 6: Print fact variable.
Step 7: Stop

C program to find factorial of a given number.

C program to find factorial of a given number. Factorial of number n is defined as follow:

      n! = 1 * 2 * 3 * 4 * ....* n 

#include<stdio.h>
int main()
{
   int i, n;
   double fact=1;
    
printf("Enter number (n): ");
   scanf("%d",&n);

   if (n < 0)
      printf("Factorial is not possible for negative number.");
   else
   {
      for(i=1; i<=n; i++)
      {
          fact = fact * i;     
      }
      printf("Factorial of number %d = %f", n, fact);
   }
}

5. Problem Definition: Write an algorithm for dividing given two numbers.

Step 1: Start.
Step 2: Read two numbers A and B.
Step 3: Answer = A / B.
Step 4: Display Answer.
Step 5: Stop


C programs of known algorithms


Bubble sort algorithm implementation.

#include<stdio.h>
int main()
{
     int i, j, n, temp, data[10];
     printf("Enter total numbers to be sorted:");
     scanf("%d",&n);
     //This program will be able to sort max 10 numbers.
    
     for(i=0; i<n; i++)
     {
           printf("Enter data[%d]:",i);
           scanf("%d",&data[i]);
     }
     printf("Unsorted data:");
     for(i=0; i<n; i++)
           printf("%d, ", data[i]);
    
     for(i=0; i<n; i++)
     {
           for(j=0; j<n-i-1; j++)
           {
                if(data[j] > data[j+1])
                {
                     temp = data[j];
                     data[j] = data[j+1];
                     data[j+1] = temp;
                }
                    
           }
     }
    
     printf("\nSorted data:");
     for(i=0; i<n; i++)
           printf("%d, ", data[i]);
     return 0;
}



Output of the program:

Enter total numbers to be sorted:5
Enter data[0]:1
Enter data[1]:3
Enter data[2]:2
Enter data[3]:4
Enter data[4]:5
Unsorted data:1, 3, 2, 4, 5,
Sorted data:1, 2, 3, 4, 5,

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