stl算法實現（lower_bound,upper_bound,binary_search，find，find_if,next_premutation,prev_premutation)...

[TOC] # 解釋 - lower_bound 可插入value的第一個位置 - upper_bound 可插入value的最後一個合適的位置 # lower_bound ``` template<typename ForwardIterator,typename T,typename Distance> inline ForwardIterator __mylower_bound(ForwardIterator first, ForwardIterator second, const T &value, Distance *, forward_iterator_tag); { Distance len = 0; distance(first, second, len); Distance half; ForwardIterator middle; while (len > 0) { half = len >> 1; middle = first; advance(middle, half); if (*middle < value) { first = middle; ++first; len = len - half - 1; } else { len = half; } } return first; } template<typename ForwardIterator,typename T> inline ForwardIterator mylower_bound(ForwardIterator first, ForwardIterator second, const T &value) { return __mylower_bound(first, second, value, distance_type(first), iterator_category(first)); } ``` # upper_bound ``` template<typename ForwardIterator, typename T, typename Distance> inline ForwardIterator __myupper_bound(ForwardIterator first, ForwardIterator second, const T &value, Distance *, forward_iterator_tag); { Distance len = 0; distance(first, second, len); Distance half; ForwardIterator middle; while (len > 0) { half = len >> 1; middle = first; advance(middle, half); if (value < *middle) { len = half; } else { first = middle; ++first; len = len - half - 1; } } return first; } template<typename ForwardIterator, typename T> inline ForwardIterator myupper_bound(ForwardIterator first, ForwardIterator second, const T &value) { return __myupper_bound(first, second, value, distance_type(first), iterator_category(first)); } ``` # binary_search ``` template<typename ForwardIterator, typename T> inline ForwardIterator mybinary_search(ForwardIterator first, ForwardIterator second, const T &value) { ForwardIterator i = mylower_bound(first, second, value); return i != last && !(value < *i); } ``` # find ``` template<typename InputIterator,typename T> InputIterator find(InputIterator first, InputIterator last, const T &value) { while (first != last&&*first != value) ++first; return first; } ``` # find_if ``` template<typename InputIterator,typename Predicate> InputIterator find_if(InputIterator first, InputIterator last, Predicate pred) { while (first != last && !pred(*first)) ++first; return first; } ``` # next_premutation ``` template<typename BidirectionalIterator> bool mynext_premutation(BidirectionalIterator first, BidirectionalIterator last) { if (first == last) return false; BidirectionalIterator i = first; ++i; if (i == last) return false; i = last; --i; for (;;) { BidirectionalIterator ii = i; --i; if (*i < *ii) { BidirectionalIterator j = last; while (!(*i < *--j)); std::iter_swap(i, j); std::reverse(ii, last); return true; } if (i == first) { std::reverse(first, last); return false; } } } ``` # prev_premutation ``` template<typename BidirectionalIterator> bool myprev_premutation(BidirectionalIterator first, BidirectionalIterator last) { if (first == last) return false; BidirectionalIterator i = first; ++i; if (i == last) return false; i = last; --i; for (;;) { BidirectionalIterator ii = i; --i; if (*ii < *i) { BidirectionalIterator j = last; while (!(*--j < *i)); std::iter_swap(i, j); std::reverse(ii, last); return true; } if (i == first) { std::reverse(first, last); return false; } } } ``` ## premutation測試 ``` template<typename Arg,typename Result> struct unary_function { typedef Arg argument_type; typedef Result result_type; }; template<typename T> struct display:public unary_function<T,void> { void operator()(T &x) const { std::cout << " " << x;}; }; void testPremutation() { std::cout << "next:" << std::endl; int a[] = { 2,1,5,7 }; std::vector<int> v(a, a + 4); std::sort(v.begin(), v.end()); do { //std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " ")); std::for_each(v.begin(), v.end(), display<int>()); std::cout << std::endl; } while (mynext_premutation(v.begin(), v.end())); std::cout << "prev:" << std::endl; int a1[] = { 2,1,5,7 }; std::vector<int> v1(a1, a1 + 4); std::sort(v1.begin(), v1.end(),std::greater<int>()); do { //std::copy(v.begin(), v.end(), std::ostream_iterator<int>(std::cout, " ")); std::for_each(v1.begin(), v1.end(), display<int>()); std::cout << std::endl; } while (myprev_premutation(v1.begin(), v1.end())); } 結果： next: 1 2 5 7 1 2 7 5 1 5 2 7 1 5 7 2 1 7 2 5 1 7 5 2 2 1 5 7 2 1 7 5 2 5 1 7 2 5 7 1 2 7 1 5 2 7 5 1 5 1 2 7 5 1 7 2 5 2 1 7 5 2 7 1 5 7 1 2 5 7 2 1 7 1 2 5 7 1 5 2 7 2 1 5 7 2 5 1 7 5 1 2 7 5 2 1 prev: 7 5 2 1 7 5 1 2 7 2 5 1 7 2 1 5 7 1 5 2 7 1 2 5 5 7 2 1 5 7 1 2 5 2 7 1 5 2 1 7 5 1 7 2 5 1 2 7 2 7 5 1 2 7 1 5 2 5 7 1 2 5 1 7 2 1 7 5 2 1 5 7 1 7 5 2 1 7 2 5 1 5 7 2 1 5 2 7 1 2 7 5 1 2 5 7 ```