find the largest number in a list.

// Challenge: find the largest number in a list.
// Input: [3, 7, 2, 9, 4]
// Expected output: 9

// Solution 1: iterating and keeping the largest seen so far.
// An interview classic to show you know how to loop and compare.
int maxWithLoop(List<int> numbers) {
  if (numbers.isEmpty) {
    throw ArgumentError('The list cannot be empty');
  }
  var largest = numbers[0];
  for (final number in numbers) {
    if (number > largest) {
      largest = number;
    }
  }
  return largest;
}

// Solution 2: using reduce, more idiomatic in Dart.
// reduce combines the elements two at a time with the given function.
int maxWithReduce(List<int> numbers) {
  return numbers.reduce((a, b) => a > b ? a : b);
}

void main() {
  print(maxWithLoop([3, 7, 2, 9, 4])); // 9
  print(maxWithReduce([3, 7, 2, 9, 4])); // 9
  print(maxWithLoop([-5, -1, -10])); // -1 (works with negatives)
  print(maxWithReduce([42])); // 42 (a single element)

  // Explanation:
  // The loop version starts by assuming the first element is the
  // largest and keeps updating it. The reduce version does the same, but
  // lets Dart walk through the list: it compares two at a time and keeps
  // the larger one. Watch out for the empty list: reduce would throw an
  // error, which is why in the manual version we validate first.
}