Histogram Counts as Bars - Dart Programming

Tallying a small sample into a Map<String, int> and rendering each count as a string of # characters builds a tiny histogram. The bar width is just '#' * count, which makes the proportions visible at a glance.

Program

Play the program to count six samples and render them as compact bars.

histogram.dart

void main() {
  var samples = ['red', 'blue', 'red', 'green', 'red', 'blue'];
  var counts = <String, int>{};
  for (var s in samples) {
    counts[s] = (counts[s] ?? 0) + 1;
  }
  var bars = counts.entries
      .map((e) => '${e.key}: ${'#' * e.value}')
      .toList();
  print(bars.join(' | '));
}

counter map `counts[s] = (counts[s] ?? 0) + 1` defaults missing keys to zero before adding one.

string repetition `'#' * count` repeats `#` once per occurrence, turning a tally into a tiny bar.

insertion order Default Dart maps keep insertion order, so the bars render in first-seen order.