如何用Java编写一个输出小于n的完美数字的函数？

Question

I am attempting to write a function in Processing that prints out all perfect numbers less than n for my homework pset. However, I am having trouble finding an algorithm that matches the problem.

I have written a for-loop that cycles through all of the numbers between 1 and n. Since the sum of all of its divisors equals the perfect number, I made an if-statement checking the remainders of n and then adding them onto a sum variable, called "result." Then, at the end of this loop, if result equals to n, I printed it out.

void perfect(int n) {

    int result = 0; 
    for(int i = 1; i < n; i++) {
        if(n % i == 0) {
            result = result + i; 
        }
    }
    if( result == n) {
        println(n); 
    }

}

Currently, my code is not printing out anything. When I removed the if-statement towards the end, it printed out all of the values of n, but not perfect numbers. I believe that there is an error somewhere in my code that is making it so that n is never equal to "result."

Answer 1

you will have to use nested for-loop to get all the perfect numbers from 1 to n. As below:

int i, sum = 1;

System.out.print("Perfect nos from 1 to n are 1,");

for (int j = 2; j <= n; j++)
{
    sum = 1;
    for (i = 2; i < j; i++)
    {
        if (j % i == 0)
            sum = sum + i;
    }
    if (j == sum)
        System.out.print(j + ",");
}