How to multiply two long values in java

Question

I am trying to multiply two largest numbers from an array of numbers. Its working fine for small numbers.

Correct input / output - this is working:

3 10 2 8 80

Correct input / output - this is failing:

2 100000 90000
9000000000

My output is however 10000000000 instead.

Can someone tell me what is wrong in my code?

public static Long sumPairwise(Long[] numbers){

        int index=0;
        int n = numbers.length;
        for(int i=1;i<n;i++){
            if(numbers[i]>numbers[index])
                    index=i;
        }
        numbers[n-1]= numbers[index];
        index=0;
        for(int j=1;j<n-1;j++){
        if(numbers[j]>numbers[index])
                index=j;
        }
        numbers[n-2]=numbers[index];
        Long product = (numbers[n-2])*(numbers[n-1]);

    return product ;
}
public static void main(String [] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    Long numbers[] = new Long[n];
    for (int i=0;i<n;i++)
    numbers[i]= sc.nextLong();
    System.out.println(sumPairwise(numbers));

}

Answer 1

You are replacing the original number in that index with another number. That is causing the issue.

Please just simply find the max 2 numbers from below logic and multiply. Also, remember to close scanner.

Here the simple solution. This will work only for positive integers.

import java.util.Scanner;

    public class Snippet {
        public static long multiplyHighestTwoValues(Long[] numbers) {

            long maxOne = 0;
            long maxTwo = 0;
            for (long n : numbers) {
                if (maxOne < n) {
                    maxTwo = maxOne;
                    maxOne = n;
                } else if (maxTwo < n) {
                    maxTwo = n;
                }
            }

            long product = maxOne * maxTwo;
            return product;
        }

        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
            int n = sc.nextInt();
            Long numbers[] = new Long[n];
            for (int i = 0; i < n; i++)
                numbers[i] = sc.nextLong();
            System.out.println(sumPairwise(numbers));
            sc.close();

        }
    }