Big O notation, with Dart examples.

big_o.dart

// O(1)
// constant
bool isFirstElementNull(List<String> elements) {
  return elements.first == null;
}

// O(n)
// growth is linear in direct proportion to the size of the data set
bool containsValue(List<String> elements, String value) {
  for (String element in elements) {
    if (element == value) return true;
  }

  return false;
}

// O(n^2), O(n^3), etc.
// proportional to the square (or greater exponent) of the size of the data set (nested loops)
bool containsDuplicates(List<String> elements) {
  for (int outer = 0; outer < elements.length; outer++) {
    for (int inner = 0; inner < elements.length; inner++) {
      // Don't compare with self
      if (outer == inner) continue;

      if (elements[outer] == elements[inner]) return true;
    }
  }

  return false;
}

// O(2^n)
// growth doubles with each addition to the data set
int fibonacci(int number) {
  if (number <= 1) return number;
  return fibonacci(number - 2) + fibonacci(number - 1);
}

// O(log n)
// growth curve that peaks at the beginning and slowly flattens out as the size of the data set increases