STL源码剖析——STL算法之remove删除算法

来源：互联网发布：一个月淘宝可以退货吗编辑：程序博客网时间：2024/06/05 01:07
前言

由于在前文的《STL算法剖析》中，源码剖析非常多，不方便学习，也不方便以后复习，这里把这些算法进行归类，对他们单独的源码剖析进行讲解。本文介绍的STL算法中的remove删除算法，源码中介绍了函数remove、remove_copy、remove_if、remove_copy_if、unique、unique_copy。并对这些函数的源码进行详细的剖析，并适当给出使用例子，具体详见下面源码剖析。
remove移除算法源码剖析

// remove, remove_if, remove_copy, remove_copy_if//移除[first,last)区间内所有与value值相等的元素，并不是真正的从容器中删除这些元素(原容器的内容不会改变)//而是将结果复制到一个以result为起始位置的容器中。新容器可以与原容器重叠template <class _InputIter, class _OutputIter, class _Tp>_OutputIter remove_copy(_InputIter __first, _InputIter __last,                        _OutputIter __result, const _Tp& __value) {  __STL_REQUIRES(_InputIter, _InputIterator);  __STL_REQUIRES(_OutputIter, _OutputIterator);  __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,       typename iterator_traits<_InputIter>::value_type, _Tp);  for ( ; __first != __last; ++__first)//遍历容器    if (!(*__first == __value)) {//如果不相等      *__result = *__first;//赋值给新容器      ++__result;//新容器前进一个位置    }  return __result;}//移除[first,last)区间内被仿函数pred判断为true的元素,并不是真正的从容器中删除这些元素(原容器的内容不会改变)//而是将结果复制到一个以result为起始位置的容器中。新容器可以与原容器重叠template <class _InputIter, class _OutputIter, class _Predicate>_OutputIter remove_copy_if(_InputIter __first, _InputIter __last,                           _OutputIter __result, _Predicate __pred) {  __STL_REQUIRES(_InputIter, _InputIterator);  __STL_REQUIRES(_OutputIter, _OutputIterator);  __STL_UNARY_FUNCTION_CHECK(_Predicate, bool,             typename iterator_traits<_InputIter>::value_type);  for ( ; __first != __last; ++__first)//遍历容器    if (!__pred(*__first)) {//若pred判断为false      *__result = *__first;//赋值给新容器      ++__result;//新容器前进一个位置    }  return __result;}//移除[first,last)区间内所有与value值相等的元素,该操作不会改变容器大小，只是容器中元素值改变//即移除之后，重新整理容器的内容template <class _ForwardIter, class _Tp>_ForwardIter remove(_ForwardIter __first, _ForwardIter __last,                    const _Tp& __value) {  __STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);  __STL_REQUIRES_BINARY_OP(_OP_EQUAL, bool,       typename iterator_traits<_ForwardIter>::value_type, _Tp);  __STL_CONVERTIBLE(_Tp, typename iterator_traits<_ForwardIter>::value_type);  __first = find(__first, __last, __value);//利用顺序查找找出第一个与value相等的元素  _ForwardIter __i = __first;  //下面调用remove_copy  return __first == __last ? __first                            : remove_copy(++__i, __last, __first, __value);}//移除[first,last)区间内所有被pred判断为true的元素,该操作不会改变容器大小，只是容器中元素值改变//即移除之后，重新整理容器的内容template <class _ForwardIter, class _Predicate>_ForwardIter remove_if(_ForwardIter __first, _ForwardIter __last,                       _Predicate __pred) {  __STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);  __STL_UNARY_FUNCTION_CHECK(_Predicate, bool,               typename iterator_traits<_ForwardIter>::value_type);  __first = find_if(__first, __last, __pred);//利用顺序查找找出第一个与value相等的元素  _ForwardIter __i = __first;  //下面调用remove_copy_if  return __first == __last ? __first                            : remove_copy_if(++__i, __last, __first, __pred);}//上面四个移除函数举例：/*#include <iostream>     // std::cout#include <algorithm>    // std::removebool IsOdd (int i) { return ((i%2)==1); }int main () {  int myints[] = {10,20,31,30,20,11,10,20};      // 10 20 31 30 20 11 10 20  std::vector<int> myvector (8);  std::remove_copy (myints,myints+8,myvector.begin(),20); // 10 31 30 11 10 0 0 0  std::cout << "myvector contains:";  for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)std::cout << ' ' << *it;  std::cout << '\n';    // bounds of range:  int* pbegin = myints;                          // ^  int* pend = myints+sizeof(myints)/sizeof(int); // ^                       ^  pend = std::remove (pbegin, pend, 20);         // 10 31 30 11 10 ?  ?  ? // ^              ^  std::cout << "range contains:";  for (int* p=pbegin; p!=pend; ++p)std::cout << ' ' << *p;  std::cout << '\n';    std::vector<int> myvector2 (7);  std::remove_copy_if (myints,myints+7,myvector2.begin(),IsOdd);  std::cout << "myvector2 contains:";  for (std::vector<int>::iterator it=myvector2.begin(); it!=myvector2.end(); ++it)std::cout << ' ' << *it;  std::cout << '\n';    pend = std::remove_if (pbegin, pend, IsOdd);   // 10 30 10 ? ? ? ? ? // ^       ^  std::cout << "the range contains:";  for (int* p=pbegin; p!=pend; ++p)std::cout << ' ' << *p;  std::cout << '\n';    return 0;}Output:myvector contains: 10 31 30 11 10 0 0 0range contains: 10 31 30 11 10myvector2 contains: 10 30 10 10 0 0 0the range contains: 10 30 10*/// unique and unique_copytemplate <class _InputIter, class _OutputIter, class _Tp>_OutputIter __unique_copy(_InputIter __first, _InputIter __last,                          _OutputIter __result, _Tp*) {  _Tp __value = *__first;  *__result = __value;  while (++__first != __last)    if (!(__value == *__first)) {      __value = *__first;      *++__result = __value;    }  return ++__result;}//若result类型为output_iterator_tag，则调用该函数template <class _InputIter, class _OutputIter>inline _OutputIter __unique_copy(_InputIter __first, _InputIter __last,                                 _OutputIter __result,                                  output_iterator_tag) {//判断first的value_type类型，根据不同类型调用不同函数  return __unique_copy(__first, __last, __result, __VALUE_TYPE(__first));}//若result类型为forward_iterator_tag，则调用该函数template <class _InputIter, class _ForwardIter>_ForwardIter __unique_copy(_InputIter __first, _InputIter __last,                           _ForwardIter __result, forward_iterator_tag) {  *__result = *__first;//记录第一个元素  while (++__first != __last)//遍历区间  //若不存在相邻重复元素，则继续记录到目标区result    if (!(*__result == *__first))      *++__result = *__first;//记录元素到目标区  return ++__result;}////unique_copy将区间[first,last)内元素复制到以result开头的区间上，但是如果存在相邻重复元素时，只复制其中第一个元素//和unique一样，这里也有两个版本/*函数原型：equality (1)template <class InputIterator, class OutputIterator>OutputIterator unique_copy (InputIterator first, InputIterator last,                              OutputIterator result);predicate (2)template <class InputIterator, class OutputIterator, class BinaryPredicate>OutputIterator unique_copy (InputIterator first, InputIterator last,                              OutputIterator result, BinaryPredicate pred);*///版本一template <class _InputIter, class _OutputIter>inline _OutputIter unique_copy(_InputIter __first, _InputIter __last,                               _OutputIter __result) {  __STL_REQUIRES(_InputIter, _InputIterator);  __STL_REQUIRES(_OutputIter, _OutputIterator);  __STL_REQUIRES(typename iterator_traits<_InputIter>::value_type,                 _EqualityComparable);  if (__first == __last) return __result;  //根据result迭代器的类型，调用不同的函数  return __unique_copy(__first, __last, __result,                       __ITERATOR_CATEGORY(__result));}template <class _InputIter, class _OutputIter, class _BinaryPredicate,          class _Tp>_OutputIter __unique_copy(_InputIter __first, _InputIter __last,                          _OutputIter __result,                          _BinaryPredicate __binary_pred, _Tp*) {  __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool, _Tp, _Tp);  _Tp __value = *__first;  *__result = __value;  while (++__first != __last)    if (!__binary_pred(__value, *__first)) {      __value = *__first;      *++__result = __value;    }  return ++__result;}template <class _InputIter, class _OutputIter, class _BinaryPredicate>inline _OutputIter __unique_copy(_InputIter __first, _InputIter __last,                                 _OutputIter __result,                                 _BinaryPredicate __binary_pred,                                 output_iterator_tag) {  return __unique_copy(__first, __last, __result, __binary_pred,                       __VALUE_TYPE(__first));}template <class _InputIter, class _ForwardIter, class _BinaryPredicate>_ForwardIter __unique_copy(_InputIter __first, _InputIter __last,                           _ForwardIter __result,                            _BinaryPredicate __binary_pred,                           forward_iterator_tag) {  __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,     typename iterator_traits<_ForwardIter>::value_type,     typename iterator_traits<_InputIter>::value_type);  *__result = *__first;  while (++__first != __last)    if (!__binary_pred(*__result, *__first)) *++__result = *__first;  return ++__result;}//版本二template <class _InputIter, class _OutputIter, class _BinaryPredicate>inline _OutputIter unique_copy(_InputIter __first, _InputIter __last,                               _OutputIter __result,                               _BinaryPredicate __binary_pred) {  __STL_REQUIRES(_InputIter, _InputIterator);  __STL_REQUIRES(_OutputIter, _OutputIterator);  if (__first == __last) return __result;  //根据result迭代器的类型，调用不同的函数  return __unique_copy(__first, __last, __result, __binary_pred,                       __ITERATOR_CATEGORY(__result));}//移除区间[first,last)相邻连续重复的元素//unique有两个版本//功能：Removes all but the first element from every consecutive group of equivalent elements in the range [first,last)./*函数原型：equality (1)：版本一采用operator==template <class ForwardIterator>ForwardIterator unique (ForwardIterator first, ForwardIterator last);predicate (2)：版本二采用pred操作template <class ForwardIterator, class BinaryPredicate>ForwardIterator unique (ForwardIterator first, ForwardIterator last,                          BinaryPredicate pred);*///版本一template <class _ForwardIter>_ForwardIter unique(_ForwardIter __first, _ForwardIter __last) {  __STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);  __STL_REQUIRES(typename iterator_traits<_ForwardIter>::value_type,                 _EqualityComparable);  __first = adjacent_find(__first, __last);//找出第一个相邻元素的起始位置  return unique_copy(__first, __last, __first);//调用unique_copy完成操作}//版本二template <class _ForwardIter, class _BinaryPredicate>_ForwardIter unique(_ForwardIter __first, _ForwardIter __last,                    _BinaryPredicate __binary_pred) {  __STL_REQUIRES(_ForwardIter, _Mutable_ForwardIterator);  __STL_BINARY_FUNCTION_CHECK(_BinaryPredicate, bool,       typename iterator_traits<_ForwardIter>::value_type,      typename iterator_traits<_ForwardIter>::value_type);  __first = adjacent_find(__first, __last, __binary_pred);//找出第一个相邻元素的起始位置  return unique_copy(__first, __last, __first, __binary_pred);//调用unique_copy完成操作}
参考资料：
《STL源码剖析》侯捷
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