Question

I’m working on a problem on codeeval.com – http://codeeval.com/open_challenges/17/.
“Write a program to determine the largest sum of contiguous integers in a list”.

Input is a text file containing comma separated list of integers, one per line e.g.

-10, 2, 3, -2, 0, 5, -15

2,3,-2,-1,10

That input should produce 8 for the first line and 12 for the second. My answer is below, but I cannot see how to get 12 for the second line, so my question is mainly what am I missing, am I misinterpreting what’s being asked for? (I get 13 for the answer)

N.B. – I live in Ireland so this is purely for my own experience, you won’t be helping me with a job application! Also, I went through every similar question on here and couldn’t find anything relevant.

If my interpretation of the question is incorrect, all I need is a point in the right direction, not necessarily code. (As in, can someone point out how the second line evaluates to 12 and not 13)

import java.util.*;
import java.io.*;

public class largest_sum {

    public static void main(String[] args) throws Exception { 

        FileReader input = new FileReader(args[0]);
        BufferedReader bufRead = new BufferedReader(input);
        String line;

        line = bufRead.readLine();

        while(line != null) { 
            addInts(line);
            line = bufRead.readLine();
        }
        bufRead.close();
        System.exit(0);
    }

    public static void addInts(String line) {
        String[] numbers = line.split(",");
        Integer largest = Integer.parseInt(numbers[0].trim());
        Integer secondLargest = 0;
        for(String s : numbers) {
            Integer converted = Integer.parseInt(s.trim());
            if(converted > largest) {

                secondLargest =  largest;
                largest = converted;
            }
        }
        System.out.println(largest + secondLargest);
    }
}

Answer 1

I would suggest having a look at Kadane’s algorithm.

Edit: As @Paolo and @Vlad pointed out – you’re not getting the correct result because you are adding the largest two numbers, as opposed to looking for a sequence. Kadane’s algorithm finds the largest sum of a sequence by first finding the largest sum ending at each position in your data set.