sdk/pkg/collection/test/priority_queue_test.dart

// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// Tests priority queue implementations utilities.

import "package:collection/priority_queue.dart";
import "package:unittest/unittest.dart";

void main() {
  testInt(() => new HeapPriorityQueue<int>());
  testCustom((comparator) => new HeapPriorityQueue<C>(comparator));
}

void testInt(PriorityQueue<int> create()) {
  for (int count in [1, 5, 127, 128]) {
    testQueue("int:$count",
              create,
              new List<int>.generate(count, (x) => x),
              count);
  }
}

void testCustom(PriorityQueue<C> create(comparator)) {
  for (int count in [1, 5, 127, 128]) {
    testQueue("Custom:$count/null",
              () => create(null),
              new List<C>.generate(count, (x) => new C(x)),
              new C(count));
    testQueue("Custom:$count/compare",
              () => create(compare),
              new List<C>.generate(count, (x) => new C(x)),
              new C(count));
    testQueue("Custom:$count/compareNeg",
              () => create(compareNeg),
              new List<C>.generate(count, (x) => new C(count - x)),
              new C(0));
  }
}

/**
 * Test that a queue behaves correctly.
 *
 * The elements must be in priority order, from highest to lowest.
 */
void testQueue(String name, PriorityQueue create(), List elements, notElement) {
  test(name, () => testQueueBody(create, elements, notElement));
}

void testQueueBody(PriorityQueue create(), List elements, notElement) {
  PriorityQueue q = create();
  expect(q.isEmpty, isTrue);
  expect(q, hasLength(0));
  expect(() { q.first; }, throwsStateError);
  expect(() { q.removeFirst(); }, throwsStateError);

  // Tests removeFirst, first, contains, toList and toSet.
  void testElements() {
    expect(q.isNotEmpty, isTrue);
    expect(q, hasLength(elements.length));

    expect(q.toList(), equals(elements));
    expect(q.toSet().toList(), equals(elements));

    for (int i = 0; i < elements.length; i++) {
      expect(q.contains(elements[i]), isTrue);
    }
    expect(q.contains(notElement), isFalse);

    List all = [];
    while (!q.isEmpty) {
      var expected = q.first;
      var actual = q.removeFirst();
      expect(actual, same(expected));
      all.add(actual);
    }

    expect(all.length, elements.length);
    for (int i = 0; i < all.length; i++) {
      expect(all[i], same(elements[i]));
    }

    expect(q.isEmpty, isTrue);
  }

  q.addAll(elements);
  testElements();

  q.addAll(elements.reversed);
  testElements();

  // Add elements in a non-linear order (gray order).
  for (int i = 0, j = 0; i < elements.length; i++) {
    int gray;
    do {
      gray = j ^ (j >> 1);
      j++;
    } while (gray >= elements.length);
    q.add(elements[gray]);
  }
  testElements();

  // Add elements by picking the middle element first, and then recursing
  // on each side.
  void addRec(int min, int max) {
    int mid = min + ((max - min) >> 1);
    q.add(elements[mid]);
    if (mid + 1 < max) addRec(mid + 1, max);
    if (mid > min) addRec(min, mid);
  }
  addRec(0, elements.length);
  testElements();

  // Test removeAll.
  q.addAll(elements);
  expect(q, hasLength(elements.length));
  Iterable all = q.removeAll();
  expect(q.isEmpty, isTrue);
  expect(all, hasLength(elements.length));
  for (int i = 0; i < elements.length; i++) {
    expect(all, contains(elements[i]));
  }

  // Test the same element more than once in queue.
  q.addAll(elements);
  q.addAll(elements.reversed);
  expect(q, hasLength(elements.length * 2));
  for (int i = 0; i < elements.length; i++) {
    var element = elements[i];
    expect(q.contains(element), isTrue);
    expect(q.removeFirst(), element);
    expect(q.removeFirst(), element);
  }

  // Test queue with all same element.
  var a = elements[0];
  for (int i = 0; i < elements.length; i++) {
    q.add(a);
  }
  expect(q, hasLength(elements.length));
  expect(q.contains(a), isTrue);
  expect(q.contains(notElement), isFalse);
  q.removeAll().forEach((x) => expect(x, same(a)));

  // Test remove.
  q.addAll(elements);
  for (var element in elements.reversed) {
    expect(q.remove(element), isTrue);
  }
  expect(q.isEmpty, isTrue);
}


// Custom class.
// Class is comparable, comparators match normal and inverse order.
int compare(C c1, C c2) => c1.value - c2.value;
int compareNeg(C c1, C c2) => c2.value - c1.value;

class C implements Comparable {
  final int value;
  const C(this.value);
  int get hashCode => value;
  bool operator==(Object other) => other is C && value == other.value;
  int compareTo(C other) => value - other.value;
  String toString() => "C($value)";
}