Problem: 2062C - Cirno and Operations
Language: java

Solution 1 (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();
    }
}

Solution 2 (runtime: 312 ms):
import java.io.*;
import java.util.*;

public class TestCodeforces {
    public static void main(String[] args) {
        IO io = new IO();
        int t = io.nextInt();

        while (t-- > 0) {
            solve(io);
        }
        io.flush();
        io.close();
    }

    public static void solve(IO io) {
        int n = io.nextInt();
        long[] arr = io.nextLongArray(n);
        long ans = Long.MIN_VALUE;
        int now = n;
        for (int k = 0; k < n; k++) {
            // calc sum
            long sum = 0;
            for (int i = 0; i < now; i++)
                sum += arr[i];
            if (k == 0) {
                ans = Math.max(ans, sum);
            } else {
                ans = Math.max(ans, Math.max(sum, -sum));
            }
            for (int i = 0; i < now - 1; i++) {
                arr[i] = arr[i + 1] - arr[i];
            }

            now--;
        }

        System.out.println(ans);
    }

    public static <T extends Comparable<T>> int eq(T a, T b) {
        return (a.compareTo(b) == 0) ? 1 : 0;
    }

    public static <T extends Comparable<T>> T max(T a, T b) {
        return (a.compareTo(b) > 0) ? a : b;
    }

    public static <T extends Comparable<T>> T min(T a, T b) {
        return (a.compareTo(b) < 0) ? a : b;
    }

    static class IO {
        BufferedReader br;
        StringTokenizer st;
        PrintWriter pw;

        public IO() {
            br = new BufferedReader(new InputStreamReader(System.in));
            pw = new PrintWriter(System.out);
        }

        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;
        }

        String[] nextStringArray(int n) {
            String[] arr = new String[n];
            for (int i = 0; i < n; i++) {
                arr[i] = next();
            }
            return arr;
        }

        int[] nextIntArray(int n) {
            int[] arr = new int[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextInt();
            }
            return arr;
        }

        long[] nextLongArray(int n) {
            long[] arr = new long[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextLong();
            }
            return arr;
        }

        double[] nextDoubleArray(int n) {
            double[] arr = new double[n];
            for (int i = 0; i < n; i++) {
                arr[i] = nextDouble();
            }
            return arr;
        }

        void print(Object obj) {
            pw.print(obj);
        }

        void println(Object obj) {
            pw.println(obj);
        }

        void flush() {
            pw.flush();
        }

        void close() {
            pw.close();
        }

        public void display(int[] arr) {
            for (int num : arr) {
                pw.print(num + " ");
            }
            pw.println();
        }

        public void display(long[] arr) {
            for (long num : arr) {
                pw.print(num + " ");
            }
            pw.println();
        }

        public void display(double[] arr) {
            for (double num : arr) {
                pw.print(num + " ");
            }
            pw.println();
        }

        public void display(String[] arr) {
            for (String str : arr) {
                pw.print(str + " ");
            }
            pw.println();
        }
    }
}