build method

void build(List<int> data)

Implementation

void build(List<int> data) {
  final freq = <int, int>{};
  for (var b in data) {
    freq[b] = (freq[b] ?? 0) + 1;
  }
  final heap = <_Node>[];
  for (var e in freq.entries) {
    heap.add(_Node(e.key, e.value));
  }
  heap.sort();
  // simple binary heap operations
  while (heap.length > 1) {
    final a = heap.removeAt(0);
    final b = heap.removeAt(0);
    final merged = _Node(null, a.freq + b.freq, a, b);
    heap.add(merged);
    heap.sort();
  }
  _root = heap.isNotEmpty ? heap.first : null;
  _codes.clear();
  if (_root != null) _buildCodes(_root!, '');
}