Question

An integer number is said to be a perfect number if it is equal to the sum of its factors (divisors), including 1 (but not the number itself). For example, 6 is a perfect number because 6 = 3+2+1. Write a C function isPerfect that returns true if the input integer number is a perfect number and false otherwise. Then, use this function in a C program that determines and prints all the perfect numbers between 1 and 1000.

Answer 1

#include <stdio.h>

int isPerfect(int n) {
    int sum = 0, i;
    for(i = 1; i < n; ++i) {
        if(n % i == 0) {
            sum += i;
        }
    }
    return sum == n;
}

int main() {
    int i;
    printf("Perfect numbers are: ");
    for (i = 1; i <= 1000; ++i) {
        if (isPerfect(i)) {
            printf("%d ", i);
        }
    }
    printf("\n");
    return 0;
}