Function test1

code/data-structures/fenwick_tree.test.cpp:3–39

/* Field testing: POJ 3468 */

void test1() {
  fenwick_tree ft(20);

  for (int i = 0; i < 20; i++) {
    assert_equal(0, ft.rsq(i, i));
    ft.update(i, i);
    assert_equal(i, ft.rsq(i, i));
    ft.update(i, -i);
    assert_equal(0, ft.rsq(i, i));
  }

  ft.update(3, 1);
  for (int i = 0; i < 20; i++)
  {
    for (int j = i; j < 20; j++)
    {
      if (i <= 3 && 3 <= j)
      {
        assert_equal(1, ft.rsq(i, j));
      }
      else
      {
        assert_equal(0, ft.rsq(i, j));
      }
    }
  }

  ft.update(5, -2);
  assert_equal(-1, ft.rsq(1, 8));
  ft.update(4, 5);
  assert_equal(4, ft.rsq(1, 8));
  ft.update(0, 100);
  assert_equal(4, ft.rsq(1, 8));
  assert_equal(104, ft.rsq(0, 19));
  ft.update(19, -200);
  assert_equal(-96, ft.rsq(0, 19));
}

struct fake_fenwick_tree {
  vi arr;