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: 281 ms):
import javax.swing.tree.TreeNode;
import java.io.*;
import java.util.*;

/**
 * @Author: _Djhhh
 * @Introduction：
 */

public class Main {
    static FastReader fr = new FastReader();
    static FastWriter fw = new FastWriter();

    public static void solve() {
        int n=fr.nextInt();
        long ans=0;
        long[] arr = new long[n];
        for(int i=0;i<n;i++){
            arr[i]= fr.nextLong();
            ans+=arr[i];
        }
        if(n==1){
            fw.println(ans);
            return;
        }
        for(int i=0;i<n-1;i++){
            long mid=0;
            for(int j=0;j<n-i-1;j++){
                arr[j]-=arr[j+1];
                mid+=arr[j];
            }
            ans=Math.max(ans,Math.max(mid,-mid));
        }
        fw.println(ans);
    }

    public static void main(String[] args) {
        int t = 1;
       t = fr.nextInt();
        while (t-- > 0) solve();
    }
}

class DSU {
    int n;
    int[] fa;
    int[] dep;
    int[] siz;
    int[] edges;
    boolean[] v;
    DSU(int n) {
        fa = new int[n];
        dep = new int[n];
        siz = new int[n];
        edges = new int[n];
        v = new boolean[n];
        for (int i = 0; i < n; i++) {
            fa[i] = i;
            dep[i] = 0;
            siz[i] = 1;
            edges[i] = 0;
            v[i]=false;
        }
    }
    int look(int x) {
        if (fa[x] == x) return x;
        else return fa[x] = look(fa[x]);
    }
    void merge(int x, int y) {
        v[x]=v[y]=true;
        int xx = look(x);
        int yy = look(y);
        if (xx == yy) return;
        edges[xx] += edges[yy] + 1;
        siz[xx] += siz[yy];
        if (dep[xx] < dep[yy]) {
            fa[xx] = yy;
        } else {
            fa[yy] = xx;
        }

        if (dep[xx] == dep[yy]) dep[xx]++;
    }
    boolean isMerge(int x, int y) {
        return look(x) == look(y);
    }
    int getSize(int x) {
        return siz[look(x)];
    }
    int getEdges(int x) {
        return edges[look(x)];
    }
}
class Pair<T1, T2> {
    private T1 first;
    private T2 second;

    public Pair(T1 first, T2 second) {
        this.first = first;
        this.second = second;
    }
    public void setFirst(T1 first) {
        this.first=first;
    }

    public void setSecond(T2 second) {
        this.second=second;
    }
    public T1 getFirst() {
        return first;
    }

    public T2 getSecond() {
        return second;
    }
}
class Algorithm {
    /**
     * 查找第一个大于等于 x 的位置
     * @param arr 查找数组
     * @param x 值
     * @param L 左边界
     * @param R 右边界
     * @return 第一个大于等于 x 的位置
     */
    public static int lowBs(int[] arr, long x, int L, int R){
        int l = L;
        int r = R;
        int res = R + 1;
        while(l <= r){
            int mid = l+r>>1;
            if(arr[mid] >= x){
                res = mid;
                r = mid - 1;
            }
            else{
                l = mid + 1;
            }
        }
        return res;
    }

    /**
     * 查找第一个大于 x 的位置
     * @param arr 查找数组
     * @param x 值
     * @param L 左边界
     * @param R 右边界
     * @return 第一个大于 x 的位置
     */
    public static int highBs(int[] arr, long x, int L, int R) {
        int l = L;
        int r = R;
        int res = R + 1;
        while(l <= r){
            int mid = l+r>>1;
            if(arr[mid] > x){
                res = mid;
                r = mid -1;
            }
            else{
                l = mid +1;
            }
        }
        return res;
    }
}
class FastReader {
    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        String str = "";
        try {
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
    }

    int[] nextIntArray() {
        String line = nextLine();
        String[] strNums = line.split("\\s+");
        int[] arr = new int[strNums.length];
        for (int i = 0; i < strNums.length; i++) {
            arr[i] = Integer.parseInt(strNums[i]);
        }
        return arr;
    }

    long[] nextLongArray() {
        String line = nextLine();
        String[] strNums = line.split("\\s+");
        long[] arr = new long[strNums.length];
        for (int i = 0; i < strNums.length; i++) {
            arr[i] = Long.parseLong(strNums[i]);
        }
        return arr;
    }

    char[] nextCharArray() {
        String line = nextLine();
        String[] strNums = line.split("\\s+");
        char[] arr = new char[strNums.length];
        for (int i = 0; i < strNums.length; i++) {
            arr[i] = strNums[i].charAt(0);
        }
        return arr;
    }

    char[] StringtoChar() {
        String line = nextLine();
        return line.toCharArray();
    }
}
class FastWriter {
    private final PrintWriter writer;

    public FastWriter() {
        writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)), true);
    }

    public void print(Object object) {
        writer.print(object);
    }

    public void println(Object object) {
        writer.println(object);
    }

    public void flush() {
        writer.flush();
    }
}