Problem: 2062C - Cirno and Operations
Language: java

Solution 1 (runtime: 218 ms):
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Olynpiade3 {
    static FastScanner scan = new FastScanner(new InputStreamReader(System.in));
    public static void main(String[] args) {
        int t = scan.nextInt();
        for (int i = 0; i < t; i++)
            solve();
    }
    static void solve(){
        int n = scan.nextInt();
        long[] posl = new long[n];
        posl[0] = scan.nextInt();
        int pos;
        long sum1 = 0, sum2 = 0, max = posl[0];
        for (int i = 1; i < n; i++){
            posl[i] = scan.nextInt();
            max += posl[i];
            sum1 += posl[i] - posl[i-1];
            sum2 += posl[i-1] - posl[i];
        }
        //System.out.println(Arrays.toString(posl) + " " + sum1 + " " + sum2 + " " + max);
        int znak;
        long sum;
        for (int i = 0; i < n - 1; i++){
            pos = 1;
            if (sum1 > sum2){
                znak = 1;
            }else
                znak = -1;
            posl[0] = (long) znak * (posl[1] - posl[0]);
            sum1 = 0; sum2 = 0; sum = posl[0];
            if (n - 1 >= 2)
                while (pos != n - i - 1){
                    pos++;
                    posl[pos - 1] = (long) znak * (posl[pos] - posl[pos-1]);
                    sum += posl[pos - 1];
                    sum1 += posl[pos - 1] - posl[pos - 2];
                    sum2 += posl[pos - 2] - posl[pos - 1];
                    //System.out.println(Arrays.toString(posl));
                }

            if (sum > max)
                max = sum;
            //System.out.println(Arrays.toString(posl));
        }
        System.out.println(max);
    }
}


class FastScanner

{

    private BufferedReader br;

    private StringTokenizer st;



    public FastScanner(InputStreamReader reader)

    {

        br = new BufferedReader(reader);

    }



    public String next()

    {

        while (st == null || !st.hasMoreTokens())

        {

            try

            {

                st = new StringTokenizer(br.readLine());

            } catch (Exception e)

            {

                e.printStackTrace();

            }

        }

        return st.nextToken();

    }



    public int nextInt()

    {

        return Integer.parseInt(next());

    }



    public double nextDouble()

    {

        return Double.parseDouble(next());

    }



    public void close() throws Exception

    {

        br.close();

    }

}

Solution 2 (runtime: 280 ms):
import java.util.*;
public class Solution{
    static int max=0;
    public static long sumCalc(ArrayList<Long> list){
        long sum=0;
        int i=1;
                
         while(i<list.size()){
            long v=list.get(i)-list.get(i-1);
            list.set(i-1,v);
            sum+=v;
            i++;
        }
        
        list.remove(list.size()-1);
        
        return sum;
    }
    public static void main(String args[]){
        Scanner sc=new Scanner(System.in);
        
        int t=sc.nextInt();
        
        for(int test=0;test<t;test++){
            int n=sc.nextInt();
            ArrayList<Long> list=new ArrayList<>();
           
            long sum=0;
            for(int i=0;i<n;i++){
                long val=sc.nextLong();
                list.add(val);
                sum+=val;
            }
            
            long max=sum;
            while(list.size()>1){
                long ans=sumCalc(list);
                max=Math.max(ans,max);
                sum=0;
                for(int i=0;i<list.size();i++){
                    sum+=(-1)*list.get(i);
                }
                
                max=Math.max(sum,max);
            }
            
            System.out.println(max);
        }
    }
}