Problem: 2050B - Transfusion
Language: java

Solution 1 (runtime: 343 ms):
 import java.io.*;
import java.math.BigInteger;
import java.util.*;
public class Main{
    public static void main(String[] args) throws IOException{
        Scanner sc= new Scanner(System.in);
        int t = sc.nextInt();
        for(int i=0;i<t;i++){
            int n = sc.nextInt();
            long ceve = 0;
            long codd = 0;
            long eve = 0;
            long odd = 0;
            for(int j =0;j<n;j++){
                long num = sc.nextLong();
                if(j%2==0){
                    odd = odd + num;
                    codd++;
                } 
                else{
                    eve = eve + num; 
                    ceve++;
                }
            }
            if(eve%ceve == 0 && odd%codd==0){
            long m = eve/ceve;
            long l = odd/codd;
            if(m==l){
                System.out.println("YES");
            }
            else{
                System.out.println("NO");
            }
        }
        else{
            System.out.println("NO");
        }
        }
    }
}
class Scanner {
  StringTokenizer st;
  BufferedReader br;

  public Scanner(InputStream s) {
      br = new BufferedReader(new InputStreamReader(s));
  }

  public Scanner(File s) throws FileNotFoundException {
      br = new BufferedReader(new FileReader(s));
  }

  public String next() throws IOException {
      while (st == null || !st.hasMoreTokens()) st = new StringTokenizer(br.readLine());
      return st.nextToken();
  }

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

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

  public String nextLine() throws IOException {
      return br.readLine();
  }
  public int[] nextArr(int n) throws IOException {
      int[] a = new int[n];
      for (int i = 0; i < n; i++) {
          a[i] = nextInt();
      }
      return a;
  }

  public double nextDouble() throws IOException {
      String x = next();
      StringBuilder sb = new StringBuilder("0");
      double res = 0, f = 1;
      boolean dec = false, neg = false;
      int start = 0;
      if (x.charAt(0) == '-') {
          neg = true;
          start++;
      }
      for (int i = start; i < x.length(); i++)
          if (x.charAt(i) == '.') {
              res = Long.parseLong(sb.toString());
              sb = new StringBuilder("0");
              dec = true;
          } else {
              sb.append(x.charAt(i));
              if (dec) f *= 10;
          }
      res += Long.parseLong(sb.toString()) / f;
      return res * (neg ? -1 : 1);
  }

  public boolean ready() throws IOException {
      return br.ready();
  }


}
class Pair implements Comparable{
    long a;
    long b;
    public Pair(long a,long b){
        this.a = a;
        this.b = b;
    }
    public int compareTo(Object o) {
        if(((Pair)o).a > a){
            return -1;
        }
        else if(((Pair)o).a < a){
            return 1;
        }
        else{
            if(((Pair)o).b > b){
                return 1;
            }
            else if(((Pair)o).b < b){
                return -1;
            }
            else{
                return 0;
            }

        }
    }
    public String toString(){
        return a + " " + b;
    }
}

Solution 2 (runtime: 202 ms):
import java.io.*;

import java.util.*;



public class Code {



    // Input and Output

    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

    static PrintWriter out = new PrintWriter(System.out);



    // For parsing integers, longs, and strings efficiently

    static StringTokenizer st;



    // Entry point

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

        int t; // Number of test cases

        t = nextInt(); // Uncomment this line if multiple test cases

        while (t-- > 0) {

            solve(); // Call the solve function for each test case

        }

        out.close(); // Close the output stream

    }







    // Solve function for each test case



    static void solve() throws IOException {

        int n = nextInt();



        int[] arr= new int[n];

        long evensum = 0,oddsum=0;



        for(int i=0;i<n;i++){

            arr[i] = nextInt();



            if(i%2==0){

                evensum+=arr[i];

            }

            else{

                oddsum+= arr[i];

            }

        }

        int evencount = n%2==0?n/2:n/2+1;

        boolean flag = true;



        if((evensum+oddsum)%n == 0){

            if( !(evensum%evencount == 0 && evensum/evencount == (evensum+oddsum)/n &&  oddsum%(n-evencount) == 0 && oddsum/(n-evencount) == (evensum+oddsum)/n) ){

                flag =false;

            }

        }

        else{

            flag = false;

        }



        out.println(flag?"YES":"NO");



    }



    // Utility methods for faster input

    static String next() throws IOException {

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

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

        }

        return st.nextToken();

    }



    static int nextInt() throws IOException {

        return Integer.parseInt(next());

    }



    static long nextLong() throws IOException {

        return Long.parseLong(next());

    }



    static double nextDouble() throws IOException {

        return Double.parseDouble(next());

    }



    char nextChar() {

        try {

            return (char) br.read();

        } catch (IOException e) {

            e.printStackTrace();

            return '\0'; // Return null character in case of an error

        }

    }



    static String nextLine() throws IOException {

        return br.readLine();

    }



    // Utility functions

    static int gcd(int a, int b) {

        if (b == 0) return a;

        return gcd(b, a % b);

    }



    static int lcm(int a, int b) {

        return a * (b / gcd(a, b));

    }



    static boolean isPrime(int n) {

        if (n <= 1) return false;

        if (n <= 3) return true;

        if (n % 2 == 0 || n % 3 == 0) return false;

        for (int i = 5; i * i <= n; i += 6) {

            if (n % i == 0 || n % (i + 2) == 0) return false;

        }

        return true;

    }



    static long power(long x, long y, long p) {

        long res = 1;

        x = x % p;

        while (y > 0) {

            if ((y & 1) == 1)

                res = (res * x) % p;

            y = y >> 1;

            x = (x * x) % p;

        }

        return res;

    }



    public static void sort(int[] arr)

    {

        //because Arrays.sort() uses quicksort which is dumb

        //Collections.sort() uses merge sort

        ArrayList<Integer> ls = new ArrayList<Integer>();

        for(int x: arr)

            ls.add(x);

        Collections.sort(ls);

        for(int i=0; i < arr.length; i++)

            arr[i] = ls.get(i);

    }



    public static void sort(long[] arr)

    {

        //because Arrays.sort() uses quicksort which is dumb

        //Collections.sort() uses merge sort

        ArrayList<Long> ls = new ArrayList<Long>();

        for(long x: arr)

            ls.add(x);

        Collections.sort(ls);

        for(int i=0; i < arr.length; i++)

            arr[i] = ls.get(i);

    }

}