泛型算法系列29:unique()&&unique_copy()

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#算法 #iterator #vector #string #reference #each

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本文通过C++标准模板库(STL)中的算法演示了如何去除容器中连续重复的元素，并展示了如何使用自定义的unique和my_unique_copy函数实现这一功能。文章通过具体的例子说明了对整数数组和字符串数组进行排序并去除重复元素的过程。

#include <algorithm> #include <vector> #include <string> #include <iterator> #include <iostream> using namespace std; template <class Type> void print_elements( Type elem ) { cout << elem << " "; } void (*pfi)( int ) = print_elements; void (*pfs)( string ) = print_elements; /************************************************************************/ /* template<class _Iter> struct iterator_traits { // get traits from iterator _Iter typedef typename _Iter::iterator_category iterator_category; typedef typename _Iter::value_type value_type; //save type information here typedef typename _Iter::difference_type difference_type; typedef difference_type distance_type; // retained typedef typename _Iter::pointer pointer; typedef typename _Iter::reference reference; }; */ /************************************************************************/ /************************************************************************/ /* */ template<class _FwdIt> inline _FwdIt my_unique(_FwdIt _First, _FwdIt _Last) { // remove each matching previous _DEBUG_RANGE(_First, _Last); for (_FwdIt _Firstb; (_Firstb = _First) != _Last && ++_First != _Last; ) if (*_Firstb == *_First) { // copy down for (; ++_First != _Last; ) if (!(*_Firstb == *_First)) *++_Firstb = *_First; return (++_Firstb); } return (_Last); } template<class _InIt, class _OutIt> inline _OutIt my_Unique_copy(_InIt _First, _InIt _Last, _OutIt _Dest) { // copy compressing pairs that match, input iterators _DEBUG_POINTER(_Dest); typename iterator_traits<_InIt>::value_type _Val = *_First; for (*_Dest++ = _Val; ++_First != _Last; ) if (!(_Val == *_First))//if (!_Pred(_Val, *_First)) _Val = *_First, *_Dest++ = _Val; return (_Dest); } /************************************************************************/ int main() { int ia[] = { 0, 1, 0, 2, 0, 3, 0, 4, 0, 5 }; vector< int > vec( ia, ia + 10 ); vector< int >::iterator vec_iter; // results in unchanged sequence: 0s are not consecutive // generates: 0 1 0 2 0 3 0 4 0 5 vec_iter = my_unique( vec.begin(), vec.end() ); for_each( vec.begin(), vec.end(), pfi ); cout << "/n/n"; // sort vector: 0 0 0 0 0 1 2 3 4 5 // then apply unique: // generates: 0 1 2 3 4 5 2 3 4 5 sort( vec.begin(), vec.end() ); vec_iter = unique( vec.begin(), vec.end() ); for_each( vec.begin(), vec.end(), pfi ); cout << "/n/n"; // erase the invalid elements from container // generates: 0 1 2 3 4 5 vec.erase( vec_iter, vec.end() ); for_each( vec.begin(), vec.end(), pfi ); cout << "/n/n"; string sa[] = { "enough", "is", "enough", "enough", "is", "good" }; vector< string > svec( sa, sa + 6 ); vector< string > vec_result( svec.size() ); vector< string >::iterator svec_iter; sort( svec.begin(), svec.end() ); svec_iter = my_Unique_copy( svec.begin(), svec.end(), vec_result.begin() ); // generates: enough good is for_each( vec_result.begin(), svec_iter, pfs ); cout << "/n/n"; return 0; }