| Index: mojo/public/dart/third_party/collection/lib/algorithms.dart
|
| diff --git a/mojo/public/dart/third_party/collection/lib/algorithms.dart b/mojo/public/dart/third_party/collection/lib/algorithms.dart
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| new file mode 100644
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| index 0000000000000000000000000000000000000000..5ff0bb3bde148de12774ccbf85fa41ebde738784
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| --- /dev/null
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| +++ b/mojo/public/dart/third_party/collection/lib/algorithms.dart
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| @@ -0,0 +1,301 @@
|
| +// 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.
|
| +
|
| +/**
|
| + * Operations on collections.
|
| + */
|
| +library dart.pkg.collection.algorithms;
|
| +
|
| +import "dart:math" show Random;
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| +
|
| +/** Version of [binarySearch] optimized for comparable keys */
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| +int _comparableBinarySearch(List<Comparable> list, Comparable key) {
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| + int min = 0;
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| + int max = list.length;
|
| + while (min < max) {
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| + int mid = min + ((max - min) >> 1);
|
| + var element = list[mid];
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| + int comp = element.compareTo(key);
|
| + if (comp == 0) return mid;
|
| + if (comp < 0) {
|
| + min = mid + 1;
|
| + } else {
|
| + max = mid;
|
| + }
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| + }
|
| + return -1;
|
| +}
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| +
|
| +/**
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| + * Returns a position of the [key] in [sortedList], if it is there.
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| + *
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| + * If the list isn't sorted according to the [compare] function, the result
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| + * is unpredictable.
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| + *
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| + * If [compare] is omitted, it defaults to calling [Comparable.compareTo] on
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| + * the objects.
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| + *
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| + * Returns -1 if [key] is not in the list by default.
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| + */
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| +int binarySearch(List sortedList, var key,
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| + { int compare(var a, var b) }) {
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| + if (compare == null) {
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| + return _comparableBinarySearch(sortedList, key);
|
| + }
|
| + int min = 0;
|
| + int max = sortedList.length;
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| + while (min < max) {
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| + int mid = min + ((max - min) >> 1);
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| + var element = sortedList[mid];
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| + int comp = compare(element, key);
|
| + if (comp == 0) return mid;
|
| + if (comp < 0) {
|
| + min = mid + 1;
|
| + } else {
|
| + max = mid;
|
| + }
|
| + }
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| + return -1;
|
| +}
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| +
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| +
|
| +/**
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| + * Shuffles a list randomly.
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| + *
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| + * A sub-range of a list can be shuffled by providing [start] and [end].
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| + */
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| +void shuffle(List list, [int start = 0, int end = null]) {
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| + Random random = new Random();
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| + if (end == null) end = list.length;
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| + int length = end - start;
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| + while (length > 1) {
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| + int pos = random.nextInt(length);
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| + length--;
|
| + var tmp1 = list[start + pos];
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| + list[start + pos] = list[start + length];
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| + list[start + length] = tmp1;
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| + }
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| +}
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| +
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| +
|
| +/**
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| + * Reverses a list, or a part of a list, in-place.
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| + */
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| +void reverse(List list, [int start = 0, int end = null]) {
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| + if (end == null) end = list.length;
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| + _reverse(list, start, end);
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| +}
|
| +
|
| +// Internal helper function that assumes valid arguments.
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| +void _reverse(List list, int start, int end) {
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| + for (int i = start, j = end - 1; i < j; i++, j--) {
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| + var tmp = list[i];
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| + list[i] = list[j];
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| + list[j] = tmp;
|
| + }
|
| +}
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| +
|
| +/**
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| + * Sort a list using insertion sort.
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| + *
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| + * Insertion sort is a simple sorting algorithm. For `n` elements it does on
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| + * the order of `n * log(n)` comparisons but up to `n` squared moves. The
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| + * sorting is performed in-place, without using extra memory.
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| + *
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| + * For short lists the many moves have less impact than the simple algorithm,
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| + * and it is often the favored sorting algorithm for short lists.
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| + *
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| + * This insertion sort is stable: Equal elements end up in the same order
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| + * as they started in.
|
| + */
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| +void insertionSort(List list,
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| + { int compare(a, b),
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| + int start: 0,
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| + int end: null }) {
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| + // If the same method could have both positional and named optional
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| + // parameters, this should be (list, [start, end], {compare}).
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| + if (end == null) end = list.length;
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| + if (compare == null) compare = Comparable.compare;
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| + _insertionSort(list, compare, start, end, start + 1);
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| +}
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| +
|
| +/**
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| + * Internal helper function that assumes arguments correct.
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| + *
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| + * Assumes that the elements up to [sortedUntil] (not inclusive) are
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| + * already sorted. The [sortedUntil] values should always be at least
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| + * `start + 1`.
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| + */
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| +void _insertionSort(List list, int compare(a, b), int start, int end,
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| + int sortedUntil) {
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| + for (int pos = sortedUntil; pos < end; pos++) {
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| + int min = start;
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| + int max = pos;
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| + var element = list[pos];
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| + while (min < max) {
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| + int mid = min + ((max - min) >> 1);
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| + int comparison = compare(element, list[mid]);
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| + if (comparison < 0) {
|
| + max = mid;
|
| + } else {
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| + min = mid + 1;
|
| + }
|
| + }
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| + list.setRange(min + 1, pos + 1, list, min);
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| + list[min] = element;
|
| + }
|
| +}
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| +
|
| +/** Limit below which merge sort defaults to insertion sort. */
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| +const int _MERGE_SORT_LIMIT = 32;
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| +
|
| +/**
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| + * Sorts a list, or a range of a list, using the merge sort algorithm.
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| + *
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| + * Merge-sorting works by splitting the job into two parts, sorting each
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| + * recursively, and then merging the two sorted parts.
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| + *
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| + * This takes on the order of `n * log(n)` comparisons and moves to sort
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| + * `n` elements, but requires extra space of about the same size as the list
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| + * being sorted.
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| + *
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| + * This merge sort is stable: Equal elements end up in the same order
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| + * as they started in.
|
| + */
|
| +void mergeSort(List list, {int start: 0, int end: null, int compare(a, b)}) {
|
| + if (end == null) end = list.length;
|
| + if (compare == null) compare = Comparable.compare;
|
| + int length = end - start;
|
| + if (length < 2) return;
|
| + if (length < _MERGE_SORT_LIMIT) {
|
| + _insertionSort(list, compare, start, end, start + 1);
|
| + return;
|
| + }
|
| + // Special case the first split instead of directly calling
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| + // _mergeSort, because the _mergeSort requires its target to
|
| + // be different from its source, and it requires extra space
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| + // of the same size as the list to sort.
|
| + // This split allows us to have only half as much extra space,
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| + // and it ends up in the original place.
|
| + int middle = start + ((end - start) >> 1);
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| + int firstLength = middle - start;
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| + int secondLength = end - middle;
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| + // secondLength is always the same as firstLength, or one greater.
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| + List scratchSpace = new List(secondLength);
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| + _mergeSort(list, compare, middle, end, scratchSpace, 0);
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| + int firstTarget = end - firstLength;
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| + _mergeSort(list, compare, start, middle, list, firstTarget);
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| + _merge(compare,
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| + list, firstTarget, end,
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| + scratchSpace, 0, secondLength,
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| + list, start);
|
| +}
|
| +
|
| +/**
|
| + * Performs an insertion sort into a potentially different list than the
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| + * one containing the original values.
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| + *
|
| + * It will work in-place as well.
|
| + */
|
| +void _movingInsertionSort(List list, int compare(a, b), int start, int end,
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| + List target, int targetOffset) {
|
| + int length = end - start;
|
| + if (length == 0) return;
|
| + target[targetOffset] = list[start];
|
| + for (int i = 1; i < length; i++) {
|
| + var element = list[start + i];
|
| + int min = targetOffset;
|
| + int max = targetOffset + i;
|
| + while (min < max) {
|
| + int mid = min + ((max - min) >> 1);
|
| + if (compare(element, target[mid]) < 0) {
|
| + max = mid;
|
| + } else {
|
| + min = mid + 1;
|
| + }
|
| + }
|
| + target.setRange(min + 1, targetOffset + i + 1,
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| + target, min);
|
| + target[min] = element;
|
| + }
|
| +}
|
| +
|
| +/**
|
| + * Sorts [list] from [start] to [end] into [target] at [targetOffset].
|
| + *
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| + * The `target` list must be able to contain the range from `start` to `end`
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| + * after `targetOffset`.
|
| + *
|
| + * Allows target to be the same list as [list], as long as it's not
|
| + * overlapping the `start..end` range.
|
| + */
|
| +void _mergeSort(List list, int compare(a, b), int start, int end,
|
| + List target, int targetOffset) {
|
| + int length = end - start;
|
| + if (length < _MERGE_SORT_LIMIT) {
|
| + _movingInsertionSort(list, compare, start, end, target, targetOffset);
|
| + return;
|
| + }
|
| + int middle = start + (length >> 1);
|
| + int firstLength = middle - start;
|
| + int secondLength = end - middle;
|
| + // Here secondLength >= firstLength (differs by at most one).
|
| + int targetMiddle = targetOffset + firstLength;
|
| + // Sort the second half into the end of the target area.
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| + _mergeSort(list, compare, middle, end,
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| + target, targetMiddle);
|
| + // Sort the first half into the end of the source area.
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| + _mergeSort(list, compare, start, middle,
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| + list, middle);
|
| + // Merge the two parts into the target area.
|
| + _merge(compare,
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| + list, middle, middle + firstLength,
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| + target, targetMiddle, targetMiddle + secondLength,
|
| + target, targetOffset);
|
| +}
|
| +
|
| +/**
|
| + * Merges two lists into a target list.
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| + *
|
| + * One of the input lists may be positioned at the end of the target
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| + * list.
|
| + *
|
| + * For equal object, elements from [firstList] are always preferred.
|
| + * This allows the merge to be stable if the first list contains elements
|
| + * that started out earlier than the ones in [secondList]
|
| + */
|
| +void _merge(int compare(a, b),
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| + List firstList, int firstStart, int firstEnd,
|
| + List secondList, int secondStart, int secondEnd,
|
| + List target, int targetOffset) {
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| + // No empty lists reaches here.
|
| + assert(firstStart < firstEnd);
|
| + assert(secondStart < secondEnd);
|
| + int cursor1 = firstStart;
|
| + int cursor2 = secondStart;
|
| + var firstElement = firstList[cursor1++];
|
| + var secondElement = secondList[cursor2++];
|
| + while (true) {
|
| + if (compare(firstElement, secondElement) <= 0) {
|
| + target[targetOffset++] = firstElement;
|
| + if (cursor1 == firstEnd) break; // Flushing second list after loop.
|
| + firstElement = firstList[cursor1++];
|
| + } else {
|
| + target[targetOffset++] = secondElement;
|
| + if (cursor2 != secondEnd) {
|
| + secondElement = secondList[cursor2++];
|
| + continue;
|
| + }
|
| + // Second list empties first. Flushing first list here.
|
| + target[targetOffset++] = firstElement;
|
| + target.setRange(targetOffset, targetOffset + (firstEnd - cursor1),
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| + firstList, cursor1);
|
| + return;
|
| + }
|
| + }
|
| + // First list empties first. Reached by break above.
|
| + target[targetOffset++] = secondElement;
|
| + target.setRange(targetOffset, targetOffset + (secondEnd - cursor2),
|
| + secondList, cursor2);
|
| +}
|
|
|