[FIXED] How to find Number with most divisor from array

Issue

I have an array and i want to find number with most divisor. The problem is that i can find the number but i cant print how many divisor it is.

static void printDivisors(int n)
{
    for (int i=1;i<=n;i++)
        if (n%i==0)
            System.out.print(i+" ");
}


public static void main(String args[])
{
    System.out.println("The divisors of 100 are: ");
    printDivisors(100);;
}

}

Solution

First of all, you only need to check values between 1 and n/2 to find the divisors of n. You won't find a divisor between n/2 and n (except for n itself). This will effectively reduce your execution time by half.

So your divisor finding method can be improved like below to count the number of divisors of a given number.

static int getNumDivisors(int n) {
    int noOfDivisors = 0;
    for (int i = 1; i <= n / 2; i++) {
        if (n % i == 0) {
            noOfDivisors++;
        }
    }
    if (n > 1) {
        noOfDivisors++; // n itself is a divisor of n
    }
    return noOfDivisors;
}

Then you need to iterate through the numbers array given by user and find the number of divisors for each number.

While iterating you need 2 variables

• currentMaxDivisors - to store the max no of divisors you have found so far
• numWithMaxDivisors - which number had the above number of divisors

If you happen to find a new number with more divisors, you update these variables with the new values. At the end, numWithMaxDivisors variable will contain the number with maximum divisors.

static int getNumDivisors(int n) {
    int noOfDivisors = 0;
    for (int i = 1; i <= n / 2; i++) {
        if (n % i == 0) {
            System.out.print(i + " ");
            noOfDivisors++;
        }
    }
    if (n > 1) {
        noOfDivisors++; // n itself is a divisor of n
    }
    return noOfDivisors;
}

static int getNumWithMaxDivisors(int[] numbers) {
    // Assuming numbers array has at least one element
    int currentMaxDivisors = 0;
    int numWithMaxDivisors = numbers[0];
    for (int i = 0; i < numbers.length; i++) {
        int numDivisors = getNumDivisors(numbers[i]);
        if (numDivisors > currentMaxDivisors) {
            numWithMaxDivisors = numbers[i];
        }
    }
    return numWithMaxDivisors;
}

public static void main(String[] args) {
    int[] numbers = new int[]{100, 55, 67, 2003, 12};
    int numWithMaxDivisors = getNumWithMaxDivisors(numbers);
    System.out.println(numWithMaxDivisors);
}

Answered By - Udith Gunaratna
Answer Checked By - Willingham (JavaFixing Volunteer)