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packages/collection/test/algorithms_test.dart

Index: packages/collection/test/algorithms_test.dart
diff --git a/packages/collection/test/algorithms_test.dart b/packages/collection/test/algorithms_test.dart
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+// 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 algorithm utilities.
+
+import "package:collection/collection.dart";
+import "package:test/test.dart";
+import 'dart:math';
+
+void main() {
+  void testShuffle(List list) {
+    List copy = list.toList();
+    shuffle(list);
+    expect(new UnorderedIterableEquality().equals(list, copy), isTrue);
+  }
+
+  test("Shuffle 0", () {
+    testShuffle([]);
+  });
+  test("Shuffle 1", () {
+    testShuffle([1]);
+  });
+  test("Shuffle 3", () {
+    testShuffle([1, 2, 3]);
+  });
+  test("Shuffle 10", () {
+    testShuffle([1, 2, 3, 4, 5, 1, 3, 5, 7, 9]);
+  });
+  test("Shuffle shuffles", () {
+    List l = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    List c = l.toList();
+    int count = 0;
+    do {
+      shuffle(l);
+      if (!const ListEquality().equals(c, l)) return;
+      // Odds of not changing the order should be one in ~ 16! ~= 2e+13.
+      // Repeat this 10 times, and the odds of accidentally shuffling to the
+      // same result every time is disappearingly tiny.
+      count++;
+      // If this happens even once, it's ok to report it.
+      print("Failed shuffle $count times");
+      if (count == 10) fail("Shuffle didn't change order.");
+    } while (true);
+  });
+  test("Shuffle sublist", (){
+    List l = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16];
+    List c = l.toList();
+    shuffle(l, 4, 12);
+    expect(const IterableEquality().equals(l.getRange(0, 4),
+                                           c.getRange(0, 4)), isTrue);
+    expect(const IterableEquality().equals(l.getRange(12, 16),
+                                           c.getRange(12, 16)), isTrue);
+    expect(const UnorderedIterableEquality().equals(l.getRange(4, 12),
+                                                    c.getRange(4, 12)),
+           isTrue);
+
+  });
+
+  test("binsearch0", () {
+    expect(binarySearch([], 2), equals(-1));
+  });
+
+  test("binsearch1", () {
+    expect(binarySearch([5], 2), equals(-1));
+    expect(binarySearch([5], 5), equals(0));
+    expect(binarySearch([5], 7), equals(-1));
+  });
+
+  test("binsearch3", () {
+    expect(binarySearch([0, 5, 10], -1), equals(-1));
+    expect(binarySearch([0, 5, 10], 0), equals(0));
+    expect(binarySearch([0, 5, 10], 2), equals(-1));
+    expect(binarySearch([0, 5, 10], 5), equals(1));
+    expect(binarySearch([0, 5, 10], 7), equals(-1));
+    expect(binarySearch([0, 5, 10], 10), equals(2));
+    expect(binarySearch([0, 5, 10], 12), equals(-1));
+  });
+
+  test("binsearchCompare0", () {
+    expect(binarySearch([], new C(2), compare: compareC), equals(-1));
+  });
+
+  test("binsearchCompare1", () {
+    var l1 = [new C(5)];
+    expect(binarySearch(l1, new C(2), compare: compareC), equals(-1));
+    expect(binarySearch(l1, new C(5), compare: compareC), equals(0));
+    expect(binarySearch(l1, new C(7), compare: compareC), equals(-1));
+  });
+
+  test("binsearchCompare3", () {
+    var l3 = [new C(0), new C(5), new C(10)];
+    expect(binarySearch(l3, new C(-1), compare: compareC), equals(-1));
+    expect(binarySearch(l3, new C(0), compare: compareC), equals(0));
+    expect(binarySearch(l3, new C(2), compare: compareC), equals(-1));
+    expect(binarySearch(l3, new C(5), compare: compareC), equals(1));
+    expect(binarySearch(l3, new C(7), compare: compareC), equals(-1));
+    expect(binarySearch(l3, new C(10), compare: compareC), equals(2));
+    expect(binarySearch(l3, new C(12), compare: compareC), equals(-1));
+  });
+
+  test("insertionSortRandom", () {
+    Random random = new Random();
+    for (int i = 0; i < 25; i++) {
+      List list = new List(i);
+      for (int j = 0; j < i; j++) {
+        list[j] = random.nextInt(25);  // Expect some equal elements.
+      }
+      insertionSort(list);
+      for (int j = 1; j < i; j++) {
+        expect(list[j - 1], lessThanOrEqualTo(list[j]));
+      }
+    }
+  });
+
+  test("insertionSortSubRanges", () {
+    List l = [6, 5, 4, 3, 2, 1];
+    insertionSort(l, start: 2, end: 4);
+    expect(l, equals([6, 5, 3, 4, 2, 1]));
+    insertionSort(l, start: 1, end: 1);
+    expect(l, equals([6, 5, 3, 4, 2, 1]));
+    insertionSort(l, start: 4, end: 6);
+    expect(l, equals([6, 5, 3, 4, 1, 2]));
+    insertionSort(l, start: 0, end: 2);
+    expect(l, equals([5, 6, 3, 4, 1, 2]));
+    insertionSort(l, start: 0, end: 6);
+    expect(l, equals([1, 2, 3, 4, 5, 6]));
+  });
+
+  test("insertionSortSpecialCases", () {
+    List l = [6, 6, 6, 6, 6, 6];
+    insertionSort(l);
+    expect(l, equals([6, 6, 6, 6, 6, 6]));
+
+    l = [6, 6, 3, 3, 0, 0];
+    insertionSort(l);
+    expect(l, equals([0, 0, 3, 3, 6, 6]));
+  });
+
+  test("MergeSortRandom", () {
+    Random random = new Random();
+    for (int i = 0; i < 250; i += 1) {
+      List list = new List(i);
+      for (int j = 0; j < i; j++) {
+        list[j] = random.nextInt(i);  // Expect some equal elements.
+      }
+      mergeSort(list);
+      for (int j = 1; j < i; j++) {
+        expect(list[j - 1], lessThanOrEqualTo(list[j]));
+      }
+    }
+  });
+
+  test("MergeSortPreservesOrder", () {
+    Random random = new Random();
+    // Small case where only insertion call is called,
+    // larger case where the internal moving insertion sort is used
+    // larger cases with multiple splittings, numbers just around a power of 2.
+    for (int size in [8, 50, 511, 512, 513]) {
+      List list = new List(size);
+      // Class OC compares using id.
+      // With size elements with id's in the range 0..size/4, a number of
+      // collisions are guaranteed. These should be sorted so that the "order"
+      // part of the objects are still in order.
+      for (int i = 0; i < size; i++) {
+        list[i] = new OC(random.nextInt(size >> 2), i);
+      }
+      mergeSort(list);
+      OC prev = list[0];
+      for (int i = 1; i < size; i++) {
+        OC next = list[i];
+        expect(prev.id, lessThanOrEqualTo(next.id));
+        if (next.id == prev.id) {
+          expect(prev.order, lessThanOrEqualTo(next.order));
+        }
+        prev = next;
+      }
+      // Reverse compare on part of list.
+      List copy = list.toList();
+      int min = size >> 2;
+      int max = size - min;
+      mergeSort(list, start: min, end: max, compare: (a, b) => b.compareTo(a));
+      prev = list[min];
+      for (int i = min + 1; i < max; i++) {
+        OC next = list[i];
+        expect(prev.id, greaterThanOrEqualTo(next.id));
+        if (next.id == prev.id) {
+          expect(prev.order, lessThanOrEqualTo(next.order));
+        }
+        prev = next;
+      }
+      // Equals on OC objects is identity, so this means the parts before min,
+      // and the parts after max, didn't change at all.
+      expect(list.sublist(0, min), equals(copy.sublist(0, min)));
+      expect(list.sublist(max), equals(copy.sublist(max)));
+    }
+  });
+
+  test("MergeSortSpecialCases", () {
+    for (int size in [511, 512, 513]) {
+      // All equal.
+      List list = new List(size);
+      for (int i = 0; i < size; i++) {
+        list[i] = new OC(0, i);
+      }
+      mergeSort(list);
+      for (int i = 0; i < size; i++) {
+        expect(list[i].order, equals(i));
+      }
+      // All but one equal, first.
+      list[0] = new OC(1, 0);
+      for (int i = 1; i < size; i++) {
+        list[i] = new OC(0, i);
+      }
+      mergeSort(list);
+      for (int i = 0; i < size - 1; i++) {
+        expect(list[i].order, equals(i + 1));
+      }
+      expect(list[size - 1].order, equals(0));
+
+      // All but one equal, last.
+      for (int i = 0; i < size - 1; i++) {
+        list[i] = new OC(0, i);
+      }
+      list[size - 1] = new OC(-1, size - 1);
+      mergeSort(list);
+      expect(list[0].order, equals(size - 1));
+      for (int i = 1; i < size; i++) {
+        expect(list[i].order, equals(i - 1));
+      }
+
+      // Reversed.
+      for (int i = 0; i < size; i++) {
+        list[i] = new OC(size - 1 - i, i);
+      }
+      mergeSort(list);
+      for (int i = 0; i < size; i++) {
+        expect(list[i].id, equals(i));
+        expect(list[i].order, equals(size - 1 - i));
+      }
+    }
+  });
+
+  test("Reverse", () {
+    List l = [6, 5, 4, 3, 2, 1];
+    reverse(l, 2, 4);
+    expect(l, equals([6, 5, 3, 4, 2, 1]));
+    reverse(l, 1, 1);
+    expect(l, equals([6, 5, 3, 4, 2, 1]));
+    reverse(l, 4, 6);
+    expect(l, equals([6, 5, 3, 4, 1, 2]));
+    reverse(l, 0, 2);
+    expect(l, equals([5, 6, 3, 4, 1, 2]));
+    reverse(l, 0, 6);
+    expect(l, equals([2, 1, 4, 3, 6, 5]));
+  });
+}
+
+class C {
+  final int id;
+  C(this.id);
+}
+int compareC(C one, C other) => one.id - other.id;
+
+class OC implements Comparable<OC> {
+  final int id;
+  final int order;
+  OC(this.id, this.order);
+  int compareTo(OC other) => id - other.id;
+  String toString() => "OC[$id,$order]";
+}