stl_algobase.h
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stl_algobase.h// Filename: stl_algobase.h// Comment By: 凝霜// E-mail: mdl2009@vip.qq.com// Blog: http://blog.csdn.net/mdl13412// 这个文件中定义的都是一些最常用的算法, 我仅仅给出一个思路,// 不进行详尽讲解, 具体算法请参考算法书籍, 推荐《算法导论》// 另外, 对于基础薄弱的, 推荐《大话数据结构》, 此书我读了一下// 试读章节, 适合初学者学习/* * * 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// 第三个参数为什么为指针参见<stl_iterator.h>template <class ForwardIterator1, class ForwardIterator2, class T>inline void __iter_swap(ForwardIterator1 a, ForwardIterator2 b, T*){ // 这里交换的其实是内部对象 T tmp = *a; *a = *b; *b = tmp;}template <class ForwardIterator1, class ForwardIterator2>inline void iter_swap(ForwardIterator1 a, ForwardIterator2 b){ // 型别以第一个为准 __iter_swap(a, b, value_type(a));}// 进行交换操作, 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非常简单了, 由于返回的是引用, 因此可以嵌套使用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;}// 这是不支持随机访问的情况template <class InputIterator, class OutputIterator>inline OutputIterator __copy(InputIterator first, InputIterator last, OutputIterator result, input_iterator_tag){ // first != last导致要进行迭代器的比较, 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*){ // 不进行迭代器间的比较, 直接指定循环次数, 高效 for (Distance n = last - first; n > 0; --n, ++result, ++first) *result = *first; return result;}// 这是支持随机访问的情况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{ // 这里是一个仿函数. 再次派发 OutputIterator operator()(InputIterator first, InputIterator last, OutputIterator result) { return __copy(first, last, result, iterator_category(first)); }};// 提供兼容#ifdef __STL_CLASS_PARTIAL_SPECIALIZATION// 可以直接移动, 不需要额外操作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);}// 需要进行一些处理, 保证对象复制的正确性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);}// 对指针提供特化template <class T>struct __copy_dispatch<T*, T*>{ T* operator()(T* first, T* last, T* result) { // 判断其内部是否具有trivial_assignment_operator, 以进行派发 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 */// 将[first, last)拷贝到result处template <class InputIterator, class OutputIterator>inline OutputIterator copy(InputIterator first, InputIterator last, OutputIterator result){ // 此处进行函数派发操作 return __copy_dispatch<InputIterator,OutputIterator>()(first, last, result);}// 针对char字符串的特化, 效率至上, C++的设计理念inline char* copy(const char* first, const char* last, char* result){ memmove(result, first, last - first); return result + (last - first);}// 针对wchar_t字符串的特化, 效率至上, C++的设计理念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_SPECIALIZATIONtemplate <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 */// 将[first, last)的元素反向拷贝到(..., last)处, 其机制和copy非常接近, 不做说明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()以选择最高效的拷贝算法 RandomAccessIterator last = first + count; return pair<RandomAccessIterator, OutputIterator>(last, copy(first, last, result));}// 从first拷贝n个值到result处template <class InputIterator, class Size, class OutputIterator>inline pair<InputIterator, OutputIterator>copy_n(InputIterator first, Size count, OutputIterator result){ // 进行函数派发, 选咋高效版本 return __copy_n(first, count, result, iterator_category(first));}// 使用value填充[first, last)区间template <class ForwardIterator, class T>void fill(ForwardIterator first, ForwardIterator last, const T& value){ for ( ; first != last; ++first) *first = value; // 调用的是operator =(), 这个要特别注意}// 用value填充[first, first + n)的区间// 为了防止越界, 可以使用下面实例的技巧// vector<int> vec();// for (int i = 0; i < 10; ++i)// vec.push_back(i);// fill_n(inserter(iv, iv.begin()), 100, 10); // 这就可以使容器动态扩展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;}// 找到两个序列第一个失配的地方, 结果以pair返回template <class InputIterator1, class InputIterator2>pair<InputIterator1, InputIterator2> mismatch(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2){ // 遍历区间, 寻找失配点 while (first1 != last1 && *first1 == *first2) { ++first1; ++first2; } return pair<InputIterator1, InputIterator2>(first1, first2);}// 提供用户自定义的二元判别式, 其余同上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)内相等, 则返回true, 如果第二个序列有多余的元素,// 则不进行比较, 直接忽略. 如果第二个序列元素不足, 会导致未定义行为template <class InputIterator1, class InputIterator2>inline bool equal(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2){ for ( ; first1 != last1; ++first1, ++first2) if (*first1 != *first2) // 只要有一个不相等就判定为false return false; return true;}// 进行比较的操作改为用户指定的二元判别式, 其余同上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;}// 字典序比较, 非常类似字符串的比较// 具体比较方式参见STL文档, 另外strcmp()也可以参考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;}// 二元判别式自己指定, 其余同上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;}// 针对字符串的特化, 效率至上inline boollexicographical_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;}// 针对字符串的特化, 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}// 一句话概括, 这个是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; }}// 特换版本, 效率决定一切inline intlexicographical_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: 0 0
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