The implementation for exact() comes straight from the definition of exact:

bool exact(void) {
  return population(seasons()) == max_population;
  }

In a solution that pre-computes the populations, there is a somewhat easier and more efficient solution, requiring a private boolean member variable is_exact, which is set after computing the populations:

max_season = 1;
while (pop[max_season] < max) {
  max_season++;
  pop[max_season] = pop[max_season - 2] + pop[max_season - 1];
  }

is_exact = pop[max_season] == max;

bool exact(void) {
  return is_exact;
  }

In any event, the remainder of the program is:

static void q(int s, int m) {

  // Answer the question "Is the jackrabbit ecosystem with s initial rabbits
  // and m maximum rabbits exact?"

  jackrabbit_ecosystem jre(s, m);

  cout << s << " " << m;

  if (!jre.exact())
    cout << " not";

  cout << " exact\n";
  }


int main() {
  q(522, 1045);
  q(74, 1000);
  q(13, 100);
  }

This page last modified on 3 July 2001.