SansaAndXOR.java

/**
 * https://www.hackerrank.com/challenges/sansa-and-xor/problem #bit-manipulation
 * #dynamic-programming XOR mindset / method DP, ..
 *
 * <p>a[0] + a[1] + a[2] + (a[0] + a[1]) + (a[1] + a[2]) + (a[0] + a[1] + a[2]) -> a[0] + a[0] +
 * a[0] + a[1] + a[1] + a[1] + a[1] + a[2] + a[2] + a[2]
 *
 * <p>find number of array that contains that elements.
 *
 * <p>Explain: i-th
 *
 * <p>N
 *
 * <p>i-1 i n-i
 *
 * <p>(i) * (n + 1 - i) -> number of array containing i-th
 */
import java.util.Scanner;

class SansaAndXOR {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int testcases = sc.nextInt();
    for (int t = 0; t < testcases; t++) {
      int n = sc.nextInt();
      int[] arr = new int[n];
      int num;
      for (int i = 0; i < n; i++) {
        num = sc.nextInt();
        arr[i] = num;
      }

      if (n % 2 != 0) {
        int val = 0;
        for (int i = 0; i < n; i++) {
          if (i % 2 == 0) {
            val ^= arr[i];
          }
        }
        System.out.println(val);
      } else {
        System.out.println(0);
      }
    }
  }
}