//---------------------------15/03/27----------------------------
//算法
{
/*
质变算法：会改变操作对象之值
所有的stl算法都作用在由迭代器[first,last)所标示出来的区间上。质变算法 就是
运算过程会更改区间内的元素内容
非质变算法：和质变算法相反
*/
/*
stl算法的一般形式
1>所有的泛型算法的前两个参数都是一对迭代器，通常称为first和last，用以标示算法的操作区间
2>stl习惯采用前闭后开区间，写成[first,last)，表示区间包含first到last(不包含last)
之间的所有元素。
*/
//****************************数值算法*****************************
//accumulate
//把区间中的数都 “加到” init的副本中 最后返回init副本值
template<class InputIterator, class T>
T accumulate(InputIterator first, InputIterator last, T init)
{
for(;first != last; ++first)
init = init + *first;
return init;
}
template<class InputIterator,class T, class BinaryOperation>
T accumulate(InputIterator first, InputIterator last, T init,
BinaryOperation binary_op)
{
for(;first != last; ++first)
init = binary_op(init, *first);
return init;
}
//adjacent_difference
//把区间中的数都 “减去” 前一个数 并把结果输出到一个迭代器中
template<class InputIterator, class OutputIterator>
OutputIterator adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result)
{
if(first == last) return result;
*result = *first;
return __adjacent_difference(first, last, result, value_type(first));
}
template<class InputIterator, class OutputIterator,class T>
OutputIterator __adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result, T*)
{
T value = *first;
while(++first != last)
{
T tmp = *first;
*++result = tmp - value;
value = tmp;
}
return ++result;
}
template<class InputIterator, class OutputIterator, class BinaryOperation>
OutputIterator adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result,
BinaryOperation binary_op)
{
if(first == last) return result;
*result = *first;
return __adjacent_difference(first, last, result, value_type(first),
binary_op);
}
template<class InputIterator, class OutputIterator,class T>
OutputIterator __adjacent_difference(InputIterator first, InputIterator last,
OutputIterator result, T*,
BinaryOperation binary_op)
{
T value = *first;
while(++first != last)
{
T tmp = *first;
*++result = binary_op(tmp,value);
value = tmp;
}
return ++result;
}
//inner_product
//把两个区间中的数做 “内积” 并都 “加到” init的副本中并最后返回这副本
template<class InputIterator1, class InputIterator2,class T>
T inner_product(InputIterator1 first1, InputIterator last1,
InputIterator2 first2, T init)
{
for(; first1 != last1; ++first1,++first2)
init = init + (*first1 * *first2);
return init;
}
template<class InputIterator1, class InputIterator2,class T,
class BinaryOperation1, class BinaryOperation2>
T inner_product(InputIterator1 first1, InputIterator last1,
InputIterator2 first2, T init, BinaryOperation1 binary_op1,
BinaryOperation2 binary_op2)
{
for(; first1 != last1; ++first1,++first2)
init = binary_op1(init, binary_op2(*first1, *first2));
return init;
}
//partial_sum
//把区间中的数都 累“加” 起来。 每加一次就输出一次到 指定迭代器。
template<class InputIterator, class OutputIterator>
OutputIterator partial_sum(InputIterator first, InputIterator last,
OutputIterator result)
{
if(first == last) return result;
*result = *first;
return __partial_sum(first, last, result, value_type(first));
}
template<class InputIterator, class OutputIterator,class T>
OutputIterator __partial_sum(InputIterator first, InputIterator last,
OutputIterator result, T*)
{
T value = *first;
while(++first != last)
{
value = value + *first;
*++result = value;
}
return ++result;
}
template<class InputIterator, class OutputIterator, class BinaryOperation>
OutputIterator partial_sum(InputIterator first, InputIterator last,
OutputIterator result, BinaryOperation binary_op)
{
if(first == last) return result;
*result = *first;
return __partial_sum(first, last, result, value_type(first), binary_op);
}
template<class InputIterator, class OutputIterator,class T>
OutputIterator __partial_sum(InputIterator first, InputIterator last,
OutputIterator result, T*,
BinaryOperation binary_op)
{
T value = *first;
while(++first != last)
{
value = binary_op(value, *first);
*++result = value;
}
return ++result;
}
//power
template<class T, class Interger>
inline T power(T x, Interger n)
{
return power(x,n,multiplies<T>());
}
template<class T, class Interger, class MonoidOperation>
T power(T x, Interger n, MonoidOperation op)
{
if(n == 0)
return identity_element(op);
else
{
//确定 x的m次 值， 为了不重复计算，看n是否能被 x的m次 整除，通过移位便可确定
while ((n & 1) == 0)
{
n >>= 1;
x = op(x, x);
}
//也是为了不重复计算，把x的n次拆分成2^m+2^(m-1)+2^(m-2)+...+1
//先算出1次，再算出2次，再算出4次。只要对应位置上有数，加进reslt就行，
//没有数则不加。
T result = x;
n >>= 1;
while (n != 0)
{
x = op(x, x);
if((n & 1) != 0)
result = op(result, x);
n >>= 1;
}
return result;
}
}
// itoa
//在一个区间中依次写入value value+1...
template<class ForwardIterator, class T>
void itoa(ForwardIterator first, ForwardIterator last, T value)
{
while(first != last)
*first++ = value++;
}
//****************************数值算法*****************************
//****************************基本算法*****************************
//equal
template<class InputIterator1, class InputIterator2>
inline bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2)
{
for(; first != last1; ++first1,++first2)
if(*first1 != *first2)
return false;
return true;
}
template<class InputIterator1, class InputIterator2,
class BinaryPredicate>
inline bool equal(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, BinaryPredicate binary_op)
{
for(; first != last1; ++first1,++first2)
if(!binary_op(*first1,*first2))
return false;
return true;
}
//fill
template<class ForwardIterator, class T>
void fill(ForwardIterator first, ForwardIterator last, const T& value)
{
for(; first != last; ++first)
*first = value;
}
//fill_n
//这里少了比较 first不需要和last比较来确定中止条件 所以只需要一个output迭代器
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;
}
//iter_swap
template<class ForwardIterator1, class ForwardIterator2>
inline void iter_swap(ForwardIterator1 a, ForwardIterator2 b)
{
__iter_swap(a, b, value_type(a));
}
template<class ForwardIterator1, class ForwardIterator2, class T>
inline void __iter_swap(ForwardIterator1 a, ForwardIterator2 b, T*)
{
T tmp = *a;
*a = *b;
*b = tmp;
}
//lexicographical_compare 按字典比较
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;
}
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;
}
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;
}
//max两者比较返回大值
template<class T>
inline const T& max(const T& a, const T& b)
{
return a < b ? 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;
}
//min两者比较返回小值
template<class T>
inline const T& min(const T& a, const T& b)
{
return b < a ? b : a;
}
template<class T, class Compare>
inline const T& min(const T& a, const T& b, Compare comp)
{
return comp(b,a) ? b : a;
}
//mismatch 找到第一个不匹配点
template<class InputIterator1, class InputIterator2>
pair<InputIterator1, InputIterator2> mismatch(
InputIterator1 first1,
InputIterator1 last1,
InputIterator2 first2)
{
while (first != last1 && *first1 == *first2)
{
++first1;
++first2;
}
return pair<InputIterator1, InputIterator2>(first1, first2);
}
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);
}
//swap
template<class T>
inline void swap(T& a, T& b)
{
T tmp = a;
a = b;
b = tmp;
}
//copy这个函数为了强化效率下了血本
//正常版本走这边
template<class InputIterator, class OutputIterator>
inline OutputIterator copy(InputIterator first, InputIterator last,
OutputIterator result)
{
return __copy_dispatch<InputIterator,OutputIterator>()
(first, last, result);
}
//char* wchar_t* 走这边
inline char* copy(const char* first, const char* last, char* result)
{
memmove(result, first, last - first);
return result + (last - first);
}
inline wchar_t* copy(const wchar_t* first, const wchar_t* last,
const wchar_t* result)
{
memmove(result, first, sizeof(wchar_t) * (last - first));
return result + (last - first);
}
//准备一个仿函数，用来再次特化，用仿函数可以根据传入的InputIterator来特化
//正常版本走这边
template<class InputIterator, char OutputIterator>
struct __copy_dispatch
{
OutputIterator operator()(InputIterator first, InputIterator last,
OutputIterator result)
{
//传入一个迭代器标签，区分是否是随机迭代器
return __copy(first, last, result, iterator_category(first));
}
};
//指针走这边
template<class T>
struct __copy_dispatch<T*, T*>
{
T* operator()(T* first, T* last, T* result)
{
//判断 是否 没有 assignment_operator重载操作
typedef typename __type_traits<T>::has_trivial_assignment_operator t;
return __copy_t(first, last, result, t());
}
};
//const指针走这边
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());
}
};
//input是基类，不管forward 还是bidi迭代器都走这边
template<class InputIterator, class OutputIterator>
inline OutputIterator __copy(InputIterator first, InputIterator last,
OutputIterator result, input_iterator_tag)
{
for(; first != last; ++result, ++first)
*result = *first;
return result;
}
//随机迭代器走这边
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));
}
//直接算出区间大小，根据大小来循环 不需要判断迭代是否相等，可以有效提升速度
template<class RandomAccessIterator, class OutputIterator, class Distance>
inline OutputIterator
__copy_d(RandomAccessIterator first, RandomAccessIterator last,
OutputIterator result, Distance*)
{
for(Distance n = last - first; n > 0; --n, ++result, ++first )
*result = *first;
return result;
}
//是 没有assignment_operator重载操作的话 就走这。直接复制内存
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);
}
//不是 没有assignment_operator重载操作(也就是有重载) 走这边，调用随机迭代器的copy方法
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);
}
原文地址：http://blog.csdn.net/boydfd/article/details/44707287
