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16fc4405c3
CLOSED TREE Backed out changeset 4bc102bd4067 (bug 1030446) Backed out changeset c11c8733e76a (bug 1030446) Backed out changeset addc1a7459a7 (bug 1030446) Backed out changeset 457b38b8094c (bug 1030446)
69 lines
1.9 KiB
C++
69 lines
1.9 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_BinarySearch_h
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#define mozilla_BinarySearch_h
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#include "mozilla/Assertions.h"
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#include <stddef.h>
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namespace mozilla {
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/*
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* The algorithm searches the given container |aContainer| over the sorted
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* index range [aBegin, aEnd) for an index |i| where |aContainer[i] == aTarget|.
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* If such an index |i| is found, BinarySearch returns |true| and the index is
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* returned via the outparam |aMatchOrInsertionPoint|. If no index is found,
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* BinarySearch returns |false| and the outparam returns the first index in
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* [aBegin, aEnd] where |aTarget| can be inserted to maintain sorted order.
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*
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* Example:
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*
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* Vector<int> sortedInts = ...
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*
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* size_t match;
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* if (BinarySearch(sortedInts, 0, sortedInts.length(), 13, &match))
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* printf("found 13 at %lu\n", match);
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*/
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template <typename Container, typename T>
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bool
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BinarySearch(const Container& aContainer, size_t aBegin, size_t aEnd,
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T aTarget, size_t* aMatchOrInsertionPoint)
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{
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MOZ_ASSERT(aBegin <= aEnd);
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size_t low = aBegin;
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size_t high = aEnd;
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while (low != high) {
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size_t middle = low + (high - low) / 2;
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const T& middleValue = aContainer[middle];
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MOZ_ASSERT(aContainer[low] <= aContainer[middle]);
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MOZ_ASSERT(aContainer[middle] <= aContainer[high - 1]);
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MOZ_ASSERT(aContainer[low] <= aContainer[high - 1]);
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if (aTarget == middleValue) {
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*aMatchOrInsertionPoint = middle;
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return true;
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}
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if (aTarget < middleValue) {
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high = middle;
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} else {
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low = middle + 1;
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}
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}
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*aMatchOrInsertionPoint = low;
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return false;
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}
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} // namespace mozilla
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#endif // mozilla_BinarySearch_h
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