Solution to the Equal stack challenge on Hacker Rank (https://www.hackerrank.com/challenges/equal-stacks/problem)

Result.java

import java.io.*;
import java.math.*;
import java.security.*;
import java.text.*;
import java.util.*;
import java.util.concurrent.*;
import java.util.function.*;
import java.util.regex.*;
import java.util.stream.*;
import static java.util.stream.Collectors.joining;
import static java.util.stream.Collectors.toList;

class Result {

    /*
     * Complete the 'equalStacks' function below.
     *
     * The function is expected to return an INTEGER.
     * The function accepts following parameters:
     *  1. INTEGER_ARRAY h1
     *  2. INTEGER_ARRAY h2
     *  3. INTEGER_ARRAY h3
     */

    public static int equalStacks(List<Integer> h1, List<Integer> h2, List<Integer> h3) {
    // Write your code here
        int sum1 = h1.stream().mapToInt(Integer::intValue).sum();
        int sum2 = h2.stream().mapToInt(Integer::intValue).sum();
        int sum3 = h3.stream().mapToInt(Integer::intValue).sum();
        
        int smallest = Math.min(sum1, Math.min(sum2, sum3));
        int index1 = 0;
        int index2 = 0;
        int index3 = 0;
        // (sum1 != sum2 || sum2 != sum3) implies !(sum1 == sum2 && sum2 == sum3) i.e sum1 == sum2 == sum3 is false
        while ((sum1 != sum2 || sum2 != sum3) && smallest != 0) {
            if (sum1 != smallest) {
                sum1 -= h1.get(index1++);
            }
            if (sum2 != smallest) {
                sum2 -= h2.get(index2++);
            }
            if (sum3 != smallest) {
                sum3 -= h3.get(index3++);
            }
            
            smallest = Math.min(sum1, Math.min(sum2, sum3));
        }
        
        return smallest;
        
    }
    
    

}

public class Solution {
    public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        String[] firstMultipleInput = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        int n1 = Integer.parseInt(firstMultipleInput[0]);

        int n2 = Integer.parseInt(firstMultipleInput[1]);

        int n3 = Integer.parseInt(firstMultipleInput[2]);

        List<Integer> h1 = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        List<Integer> h2 = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        List<Integer> h3 = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
            .map(Integer::parseInt)
            .collect(toList());

        int result = Result.equalStacks(h1, h2, h3);

        bufferedWriter.write(String.valueOf(result));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }
}