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program to find perfect numbers between 1 to n

program to find perfect numbers between 1 to n

Write a C program to find all Perfect numbers between 1 to n. C program to find all perfect numbers between given range. How to generate all perfect numbers between given interval using loop in C programming.

What is Perfect number?

Perfect number is a positive integer which is equal to the sum of its proper positive divisors.

For example: 6 is the first perfect number
Proper divisors of 6 are 1, 2, 3
Sum of its proper divisors = 1 + 2 + 3 = 6.
Hence 6 is a perfect number.
Logic to find all Perfect number between 1 to n

    Input upper limit from user to find Perfect numbers. Store it in a variable say end.
    Run a loop from 1 to end, increment 1 in each iteration. The loop structure should look like for(x=1; x<=end; x++).
    For each iteration inside loop print the value of x if it is a Perfect number.

#include <stdio.h>

int main()
{
    int x, j, end, sum;

    /* Input upper limit to print perfect number */
    printf("Enter upper limit: ");
    scanf("%d", &end);

    printf("All Perfect numbers between 1 to %d:\n", end);
    
    /* Iterate from 1 to end */
    for(x=1; x<=end; x++)
    {
        sum = 0;

        /* Check whether the current number x is Perfect number or not */
        for(j=1; j<x; j++)
        {
            if(x % j == 0)
            {
                sum += j;
            }
        }
 
        /* If the current number x is Perfect number */
        if(sum == x)
        {
            printf("%d, ", x);
        }
    }

    return 0;
}