Frequency Counter Pattern in Dart

main.dart

// https://dartpad.dartlang.org/6f21c9137b5b14a86025aa5d7dcb7d75

// Frequency Counter pattern in Dart

void main() {
  
  /**
   * Problem Description:
   * 
   * Write a function called same which accepts two arrays.
   * The function should return true if every value in the
   * array has its corresponding value squared in the second array.
   * The frequency of values must be the same.
   * */
  
  print("Test 1:  ${assertB(true, same([1, 2, 3], [4, 1, 9]))}");
  print('');
  print("Test 2:  ${assertB(false, same([1, 2, 3], [1, 9]))}");
  print('');
  print("Test 3:  ${assertB(false, same([1, 2, 1], [4, 4, 1]))}");
  print('');
  print("Test 4:  ${assertB(true, same([1, 2, 1], [4, 1, 1]))}");
  print('');
  print("Test 5:  ${assertB(true, same([1, 3, 3, 3, 3, 2, 1], [4, 1, 1, 9, 9, 9, 9]))}");
  print('');
  print("Test 6:  ${assertB(false, same([1, 2, 3], [4, 1, 9, 9]))}");
}

bool same(List<int>a1, List<int>a2) {
  // Early return if frequency count isn't the same
  if (a1.length != a2.length) return false;
  
  Map<int, int> m = Map();
  // {1: 2, 4: 0}

  int square;
  for (int n in a1) {
    square = n * n;
    m.update(square, (curr) => ++curr, ifAbsent: () => 1 );
  }
  
  for (int n in a2) {
    // Key must exist
    if (!m.containsKey(n)) return false;
    // If 
    int updatedValue = m.update(n, (curr) => --curr);
    
    if (updatedValue < 0) return false;
  }
  
  return true;
}



String assertB(bool b1, bool b2) {
  return b1 == b2 ? 'PASS' : 'FAIL';
}