Check If Two Numbers are Friendly Pair or Not in C Program

Check if two numbers are friendly pair or not in c program.

In this article, you will learn how to check whether or not numbers are friendly with each other.

 

Example-1

 

Example-2

 

What are the friendly numbers?

Take two input values 6 & 28

• Divisors of 6 are 1, 2, 3, 6
• Divisor of 28 are 1, 2, 4, 7, 14, 28
• (1 + 2 + 3 + 6) / 6 = 2 , and (1 + 2 + 4 + 7 + 14 + 28) / 28 = 2
• 2 == 2
• It means 6 & 28 are friendly with each other

 

There are 4 ways to solve this problem:

1. Using While loop
2. Using Do-while loop
3. Using For loop
4. Using Function

 

You should know about the following topics in C programming to understand this program:

• If-else statement
• While loop in C
• Do-while loop in C
• For loop in C
• C Functions

 

1 - Friendly Pair or Not in C Program using For loop

// Check If Two Numbers are Friendly Pair or Not in C using For loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num_1, num_2, sum_1 = 0, sum_2 = 0;
    int i;

    // Step-1 Take two input values from the User
    printf("INPUT FIRST NUMBER: ");
    scanf("%d", &num_1);

    printf("INPUT SECOND NUMBER: ");
    scanf("%d", &num_2);

    // Step-2 Calculate the divisors sum of the first number
    for (i = 1; i < num_1; i++)
    {
        if (num_1 % i == 0)
            sum_1 += i;
    }

    // Step-3 Calculate the divisors sum of the second number
    for (i = 1; i < num_2; i++)
    {
        if (num_2 % i == 0)
            sum_2 += i;
    }

    // Step-4 Compare the first number with the divisor num divided by the first number with the same process as the second number
    if (sum_1 / num_1 == sum_2 / num_2)
        printf("\n%d & %d = FRIENDLY PAIRS\n", num_1, num_2);
    else
        printf("\n%d & %d = NOT FRIENDLY PAIRS\n", num_1, num_2);

    return 0;
}

Run

Output

 

2 - Friendly Pair or Not in C Program using While loop

// Check If Two Numbers are Friendly Pair or Not in C using While loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num_1, num_2, sum_1 = 0, sum_2 = 0;
    int i;

    // Step-1 Take two input values from the User
    printf("INPUT FIRST NUMBER: ");
    scanf("%d", &num_1);

    printf("INPUT SECOND NUMBER: ");
    scanf("%d", &num_2);

    // Step-2 Calculate the divisors sum of the first number
    i = 1;
    while (i < num_1)
    {
        if (num_1 % i == 0)
            sum_1 += i;
        i++;
    }

    // Step-3 Calculate the divisors sum of the second number
    i = 1;
    while (i < num_2)
    {
        if (num_2 % i == 0)
            sum_2 += i;
        i++;
    }

    // Step-4 Compare the first number with the divisor num divided by the first number with the same process as the second number
    if (sum_1 / num_1 == sum_2 / num_2)
        printf("\n%d & %d = FRIENDLY PAIRS\n", num_1, num_2);
    else
        printf("\n%d & %d = NOT FRIENDLY PAIRS\n", num_1, num_2);

    return 0;
}

Run

Output

 

3 - Friendly Pair or Not in C Program using Do-while loop

// Check If Two Numbers are Friendly Pair or Not in C using Do-while loop
#include <stdio.h>

// It's the main function of the program
int main()
{
    int num_1, num_2, sum_1 = 0, sum_2 = 0;
    int i;

    // Step-1 Take two input values from the User
    printf("INPUT FIRST NUMBER: ");
    scanf("%d", &num_1);

    printf("INPUT SECOND NUMBER: ");
    scanf("%d", &num_2);

    // Step-2 Calculate the divisors sum of the first number
    i = 1;
    do
    {
        if (num_1 % i == 0)
            sum_1 += i;
        i++;
    } while (i < num_1);

    // Step-3 Calculate the divisors sum of the second number
    i = 1;
    do
    {
        if (num_2 % i == 0)
            sum_2 += i;
        i++;
    } while (i < num_2);

    // Step-4 Compare the first number with the divisor num divided by the first number with the same process as the second number
    if (sum_1 / num_1 == sum_2 / num_2)
        printf("\n%d & %d = FRIENDLY PAIRS\n", num_1, num_2);
    else
        printf("\n%d & %d = NOT FRIENDLY PAIRS\n", num_1, num_2);

    return 0;
}

Run

 

4 -Friendly Pair or Not in C Program using Function

// Check If Two Numbers are Friendly Pair or Not in C using Function
#include <stdio.h>

// Function to get the sum of divisors
int get_divisors_sum(int number)
{
    int sum = 0;
    for (int i = 1; i < number; i++)
    {
        if (number % i == 0)
            sum += i;
    }
    return sum;
}

// Function to calculate and check whether the friendly or not
int check_friendly_or_not(int num_1, int num_2)
{
    int sum_1 = get_divisors_sum(num_1);
    int sum_2 = get_divisors_sum(num_2);

    // Compare the first number with the divisor num divided by the first number with the same process as the second number
    if (sum_1 / num_1 == sum_2 / num_2)
        printf("\n%d & %d = FRIENDLY PAIRS\n", num_1, num_2);
    else
        printf("\n%d & %d = NOT FRIENDLY PAIRS\n", num_1, num_2);
    return 0;
}

// It's the main function of the program
int main()
{
    int num_1, num_2;

    // Step-1 Take two input values from the User
    printf("INPUT FIRST NUMBER: ");
    scanf("%d", &num_1);

    printf("INPUT SECOND NUMBER: ");
    scanf("%d", &num_2);

    // Step-2 Call the check_friendly_or_not(); function & print the final output of the program
    check_friendly_or_not(num_1, num_2);

    return 0;
}

Run

Output