// Filename: stl_algobase.h
// Comment By: 凝霜
// E-mail: mdl2009@vip.qq.com
// Blog: http://blog.csdn.net/mdl13412
// 這個檔案中定義的都是一些最常用的演算法, 我僅僅給出一個思路,
// 不進行詳盡講解, 具體演算法請參考演算法書籍, 推薦《演算法導論》
// 另外, 對於基礎薄弱的, 推薦《大話資料結構》, 此書我讀了一下
// 試讀章節, 適合初學者學習
/*
*
* Copyright (c) 1994
* Hewlett-Packard Company
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Hewlett-Packard Company makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*
* Copyright (c) 1996
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/* NOTE: This is an internal header file, included by other STL headers.
* You should not attempt to use it directly.
*/
#ifndef __SGI_STL_INTERNAL_ALGOBASE_H
#define __SGI_STL_INTERNAL_ALGOBASE_H
#ifndef __STL_CONFIG_H
#include <stl_config.h>
#endif
#ifndef __SGI_STL_INTERNAL_RELOPS
#include <stl_relops.h>
#endif
#ifndef __SGI_STL_INTERNAL_PAIR_H
#include <stl_pair.h>
#endif
#ifndef __TYPE_TRAITS_H_
#include <type_traits.h>
#endif
#include <string.h>
#include <limits.h>
#include <stdlib.h>
#include <stddef.h>
#include <new.h>
#include <iostream.h>
#ifndef __SGI_STL_INTERNAL_ITERATOR_H
#include <stl_iterator.h>
#endif
__STL_BEGIN_NAMESPACE
// 第三個引數為什麼為指標參見<stl_iterator.h>
template <class ForwardIterator1, class ForwardIterator2, class T>
inline void __iter_swap(ForwardIterator1 a, ForwardIterator2 b, T*)
{
// 這裡交換的其實是內部物件
T tmp = *a;
*a = *b;
*b = tmp;
}
template <class ForwardIterator1, class ForwardIterator2>
inline void iter_swap(ForwardIterator1 a, ForwardIterator2 b)
{
// 型別以第一個為準
__iter_swap(a, b, value_type(a));
}
// 進行交換操作, 使用的是operator =()
template <class T>
inline void swap(T& a, T& b)
{
T tmp = a;
a = b;
b = tmp;
}
#ifndef __BORLANDC__
#undef min
#undef max
// max和min非常簡單了, 由於返回的是引用, 因此可以巢狀使用
template <class T>
inline const T& min(const T& a, const T& b)
{
return b < a ? b : a;
}
template <class T>
inline const T& max(const T& a, const T& b)
{
return a < b ? b : a;
}
#endif /* __BORLANDC__ */
template <class T, class Compare>
inline const T& min(const T& a, const T& b, Compare comp)
{
return comp(b, a) ? b : a;
}
template <class T, class Compare>
inline const T& max(const T& a, const T& b, Compare comp)
{
return comp(a, b) ? b : a;
}
// 這是不支援隨機訪問的情況
template <class InputIterator, class OutputIterator>
inline OutputIterator __copy(InputIterator first, InputIterator last,
OutputIterator result, input_iterator_tag)
{
// first != last導致要進行迭代器的比較, 效率低
for ( ; first != last; ++result, ++first)
*result = *first;
return result;
}
template <class RandomAccessIterator, class OutputIterator, class Distance>
inline OutputIterator
__copy_d(RandomAccessIterator first, RandomAccessIterator last,
OutputIterator result, Distance*)
{
// 不進行迭代器間的比較, 直接指定迴圈次數, 高效
for (Distance n = last - first; n > 0; --n, ++result, ++first)
*result = *first;
return result;
}
// 這是支援隨機訪問的情況
template <class RandomAccessIterator, class OutputIterator>
inline OutputIterator
__copy(RandomAccessIterator first, RandomAccessIterator last,
OutputIterator result, random_access_iterator_tag)
{
return __copy_d(first, last, result, distance_type(first));
}
template <class InputIterator, class OutputIterator>
struct __copy_dispatch
{
// 這裡是一個仿函式. 再次派發
OutputIterator operator()(InputIterator first, InputIterator last,
OutputIterator result) {
return __copy(first, last, result, iterator_category(first));
}
};
// 提供相容
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
// 可以直接移動, 不需要額外操作
template <class T>
inline T* __copy_t(const T* first, const T* last, T* result, __true_type)
{
memmove(result, first, sizeof(T) * (last - first));
return result + (last - first);
}
// 需要進行一些處理, 保證物件複製的正確性
template <class T>
inline T* __copy_t(const T* first, const T* last, T* result, __false_type)
{
return __copy_d(first, last, result, (ptrdiff_t*) 0);
}
// 對指標提供特化
template <class T>
struct __copy_dispatch<T*, T*>
{
T* operator()(T* first, T* last, T* result)
{
// 判斷其內部是否具有trivial_assignment_operator, 以進行派發
typedef typename __type_traits<T>::has_trivial_assignment_operator t;
return __copy_t(first, last, result, t());
}
};
template <class T>
struct __copy_dispatch<const T*, T*>
{
T* operator()(const T* first, const T* last, T* result) {
typedef typename __type_traits<T>::has_trivial_assignment_operator t;
return __copy_t(first, last, result, t());
}
};
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
// 將[first, last)拷貝到result處
template <class InputIterator, class OutputIterator>
inline OutputIterator copy(InputIterator first, InputIterator last,
OutputIterator result)
{
// 此處進行函式派發操作
return __copy_dispatch<InputIterator,OutputIterator>()(first, last, result);
}
// 針對char字串的特化, 效率至上, C++的設計理念
inline char* copy(const char* first, const char* last, char* result)
{
memmove(result, first, last - first);
return result + (last - first);
}
// 針對wchar_t字串的特化, 效率至上, C++的設計理念
inline wchar_t* copy(const wchar_t* first, const wchar_t* last,
wchar_t* result) {
memmove(result, first, sizeof(wchar_t) * (last - first));
return result + (last - first);
}
template <class BidirectionalIterator1, class BidirectionalIterator2>
inline BidirectionalIterator2 __copy_backward(BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result)
{
while (first != last) *--result = *--last;
return result;
}
template <class BidirectionalIterator1, class BidirectionalIterator2>
struct __copy_backward_dispatch
{
BidirectionalIterator2 operator()(BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result)
{
return __copy_backward(first, last, result);
}
};
#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION
template <class T>
inline T* __copy_backward_t(const T* first, const T* last, T* result,
__true_type)
{
const ptrdiff_t N = last - first;
memmove(result - N, first, sizeof(T) * N);
return result - N;
}
template <class T>
inline T* __copy_backward_t(const T* first, const T* last, T* result,
__false_type)
{
return __copy_backward(first, last, result);
}
template <class T>
struct __copy_backward_dispatch<T*, T*>
{
T* operator()(T* first, T* last, T* result)
{
typedef typename __type_traits<T>::has_trivial_assignment_operator t;
return __copy_backward_t(first, last, result, t());
}
};
template <class T>
struct __copy_backward_dispatch<const T*, T*>
{
T* operator()(const T* first, const T* last, T* result)
{
typedef typename __type_traits<T>::has_trivial_assignment_operator t;
return __copy_backward_t(first, last, result, t());
}
};
#endif /* __STL_CLASS_PARTIAL_SPECIALIZATION */
// 將[first, last)的元素反向拷貝到(..., last)處, 其機制和copy非常接近, 不做說明
template <class BidirectionalIterator1, class BidirectionalIterator2>
inline BidirectionalIterator2 copy_backward(BidirectionalIterator1 first,
BidirectionalIterator1 last,
BidirectionalIterator2 result)
{
return __copy_backward_dispatch<BidirectionalIterator1,
BidirectionalIterator2>()(first, last,
result);
}
template <class InputIterator, class Size, class OutputIterator>
pair<InputIterator, OutputIterator> __copy_n(InputIterator first, Size count,
OutputIterator result,
input_iterator_tag)
{
for ( ; count > 0; --count, ++first, ++result)
*result = *first;
return pair<InputIterator, OutputIterator>(first, result);
}
template <class RandomAccessIterator, class Size, class OutputIterator>
inline pair<RandomAccessIterator, OutputIterator>
__copy_n(RandomAccessIterator first, Size count,
OutputIterator result,
random_access_iterator_tag)
{
// 使用copy()以選擇最高效的拷貝演算法
RandomAccessIterator last = first + count;
return pair<RandomAccessIterator, OutputIterator>(last,
copy(first, last, result));
}
// 從first拷貝n個值到result處
template <class InputIterator, class Size, class OutputIterator>
inline pair<InputIterator, OutputIterator>
copy_n(InputIterator first, Size count,
OutputIterator result)
{
// 進行函式派發, 選咋高效版本
return __copy_n(first, count, result, iterator_category(first));
}
// 使用value填充[first, last)區間
template <class ForwardIterator, class T>
void fill(ForwardIterator first, ForwardIterator last, const T& value)
{
for ( ; first != last; ++first)
*first = value; // 呼叫的是operator =(), 這個要特別注意
}
// 用value填充[first, first + n)的區間
// 為了防止越界, 可以使用下面例項的技巧
// vector<int> vec();
// for (int i = 0; i < 10; ++i)
// vec.push_back(i);
// fill_n(inserter(iv, iv.begin()), 100, 10); // 這就可以使容器動態擴充套件
template <class OutputIterator, class Size, class T>
OutputIterator fill_n(OutputIterator first, Size n, const T& value)
{
for ( ; n > 0; --n, ++first)
*first = value;
return first;
}
// 找到兩個序列第一個失配的地方, 結果以pair返回
template <class InputIterator1, class InputIterator2>
pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1,
InputIterator1 last1,
InputIterator2 first2)
{
// 遍歷區間, 尋找失配點
while (first1 != last1 && *first1 == *first2) {
++first1;
++first2;
}
return pair<InputIterator1, InputIterator2>(first1, first2);
}
// 提供使用者自定義的二元判別式, 其餘同上
template <class InputIterator1, class InputIterator2, class BinaryPredicate>
pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1,
InputIterator1 last1,
InputIterator2 first2,
BinaryPredicate binary_pred)
{
while (first1 != last1 && binary_pred(*first1, *first2)) {
++first1;
++first2;
}
return pair<InputIterator1, InputIterator2>(first1, first2);
}
// 如果序列在[first, last)內相等, 則返回true, 如果第二個序列有多餘的元素,
// 則不進行比較, 直接忽略. 如果第二個序列元素不足, 會導致未定義行為
template <class InputIterator1, class InputIterator2>
inline bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2)
{
for ( ; first1 != last1; ++first1, ++first2)
if (*first1 != *first2) // 只要有一個不相等就判定為false
return false;
return true;
}
// 進行比較的操作改為使用者指定的二元判別式, 其餘同上
template <class InputIterator1, class InputIterator2, class BinaryPredicate>
inline bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, BinaryPredicate binary_pred)
{
for ( ; first1 != last1; ++first1, ++first2)
if (!binary_pred(*first1, *first2))
return false;
return true;
}
// 字典序比較, 非常類似字串的比較
// 具體比較方式參見STL文件, 另外strcmp()也可以參考
template <class InputIterator1, class InputIterator2>
bool lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2)
{
for ( ; first1 != last1 && first2 != last2; ++first1, ++first2) {
if (*first1 < *first2)
return true;
if (*first2 < *first1)
return false;
}
return first1 == last1 && first2 != last2;
}
// 二元判別式自己指定, 其餘同上
template <class InputIterator1, class InputIterator2, class Compare>
bool lexicographical_compare(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
Compare comp) {
for ( ; first1 != last1 && first2 != last2; ++first1, ++first2)
{
if (comp(*first1, *first2))
return true;
if (comp(*first2, *first1))
return false;
}
return first1 == last1 && first2 != last2;
}
// 針對字串的特化, 效率至上
inline bool
lexicographical_compare(const unsigned char* first1,
const unsigned char* last1,
const unsigned char* first2,
const unsigned char* last2)
{
const size_t len1 = last1 - first1;
const size_t len2 = last2 - first2;
const int result = memcmp(first1, first2, min(len1, len2));
return result != 0 ? result < 0 : len1 < len2;
}
// 針對字串的特化, 效率至上
inline bool lexicographical_compare(const char* first1, const char* last1,
const char* first2, const char* last2)
{
#if CHAR_MAX == SCHAR_MAX
return lexicographical_compare((const signed char*) first1,
(const signed char*) last1,
(const signed char*) first2,
(const signed char*) last2);
#else
return lexicographical_compare((const unsigned char*) first1,
(const unsigned char*) last1,
(const unsigned char*) first2,
(const unsigned char*) last2);
#endif
}
// 一句話概括, 這個是strcmp()的泛化版本
template <class InputIterator1, class InputIterator2>
int lexicographical_compare_3way(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2)
{
while (first1 != last1 && first2 != last2) {
if (*first1 < *first2) return -1;
if (*first2 < *first1) return 1;
++first1; ++first2;
}
if (first2 == last2) {
return !(first1 == last1);
} else {
return -1;
}
}
// 特換版本, 效率決定一切
inline int
lexicographical_compare_3way(const unsigned char* first1,
const unsigned char* last1,
const unsigned char* first2,
const unsigned char* last2)
{
const ptrdiff_t len1 = last1 - first1;
const ptrdiff_t len2 = last2 - first2;
const int result = memcmp(first1, first2, min(len1, len2));
return result != 0 ? result : (len1 == len2 ? 0 : (len1 < len2 ? -1 : 1));
}
inline int lexicographical_compare_3way(const char* first1, const char* last1,
const char* first2, const char* last2)
{
#if CHAR_MAX == SCHAR_MAX
return lexicographical_compare_3way(
(const signed char*) first1,
(const signed char*) last1,
(const signed char*) first2,
(const signed char*) last2);
#else
return lexicographical_compare_3way((const unsigned char*) first1,
(const unsigned char*) last1,
(const unsigned char*) first2,
(const unsigned char*) last2);
#endif
}
__STL_END_NAMESPACE
#endif /* __SGI_STL_INTERNAL_ALGOBASE_H */
// Local Variables:
// mode:C++
// End: