mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-08 20:47:44 +00:00
67 lines
1.8 KiB
C++
67 lines
1.8 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
#ifndef mozilla_BinarySearch_h
|
|
#define mozilla_BinarySearch_h
|
|
|
|
#include "mozilla/Assertions.h"
|
|
|
|
#include <stddef.h>
|
|
|
|
namespace mozilla {
|
|
|
|
/*
|
|
* The algorithm searches the given container 'c' over the sorted index range
|
|
* [begin, end) for an index 'i' where 'c[i] == target'. If such an index 'i' is
|
|
* found, BinarySearch returns 'true' and the index is returned via the outparam
|
|
* 'matchOrInsertionPoint'. If no index is found, BinarySearch returns 'false'
|
|
* and the outparam returns the first index in [begin, end] where 'target' can
|
|
* be inserted to maintain sorted order.
|
|
*
|
|
* Example:
|
|
*
|
|
* Vector<int> sortedInts = ...
|
|
*
|
|
* size_t match;
|
|
* if (BinarySearch(sortedInts, 0, sortedInts.length(), 13, &match))
|
|
* printf("found 13 at %lu\n", match);
|
|
*/
|
|
|
|
template <typename Container, typename T>
|
|
bool
|
|
BinarySearch(const Container &c, size_t begin, size_t end, T target, size_t *matchOrInsertionPoint)
|
|
{
|
|
MOZ_ASSERT(begin <= end);
|
|
|
|
size_t low = begin;
|
|
size_t high = end;
|
|
while (low != high) {
|
|
size_t middle = low + (high - low) / 2;
|
|
const T &middleValue = c[middle];
|
|
|
|
MOZ_ASSERT(c[low] <= c[middle]);
|
|
MOZ_ASSERT(c[middle] <= c[high - 1]);
|
|
MOZ_ASSERT(c[low] <= c[high - 1]);
|
|
|
|
if (target == middleValue) {
|
|
*matchOrInsertionPoint = middle;
|
|
return true;
|
|
}
|
|
|
|
if (target < middleValue)
|
|
high = middle;
|
|
else
|
|
low = middle + 1;
|
|
}
|
|
|
|
*matchOrInsertionPoint = low;
|
|
return false;
|
|
}
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif // mozilla_BinarySearch_h
|