STL power算法：
template<class T , class Integer, class MonoidOperation>
T power(T x ,Iteger n, MonoidOperation op){
if(n == 0) return identity_element(op); //证同元素，如果是0的话，代表加法的正同元素
else{
while((n & 1) == 0){ //n为偶数的时候
n >>= 1;
x = op(x,x)
}
T result = x;
n >>= 1;
while(n != 0){ //n为奇数的形式
x = op(x,x);
if(n ！=0 )result = op(result, x);
n >>= 1;
}
return result;
}
}
//字符串逻辑比较的特化版
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) ); //非常好的方法，先比较公共的部分。
return result != 0? result < 0 : len1 < len2;
}
//取两个集合的并集
template<class InputIterator1 , class InputIterator2, class OutputIterator >
OutputIterator set_union(InputIterator1 first1, InputIterator last1, InputIterator first2, InputIterator last2, OutputIterator result)
{
while(first1 != last1 && first2 != last2){
if(*first1 < *first2){
*result = *first1;
++*first1;
}
else if (* first1 > *first2){
*result = *first2;
++first2;
}
else{
*result = *first1;
++first1;
++first2;
}
}
++result;
return copy(first2, last2,copy(first1, first2, result));
}
//查找满足条件的相邻元素。
template<class ForwardIterator>
ForwardIterator adjacent_find(ForwardIterator first, ForwardIterator last )
{
if(first == last) return last;
ForwardIterator next = first;
while(++next != last){
if(*first == *next)return first;
first = next;
}
return last;
}
//find_end函数，在序列一[first1,last1) 所覆盖的区间中，查找序列二[first2,last2)的最后一次出现点
ForwardIterator前向迭代器
template<class ForwardIterator1, class ForwardIterator2>
ForwardIterator1 _find_end(ForwardIterator1 first1, ForwardIterator1 last1,ForwardIterator2 first2, ForwardIterator2 last2, forward_iterator_tag, forward_iterator_tag)
{
if(first2 == last2)return last1;
else{
ForwardIterator1 result = last1;
while(1){
ForwardIterator1 new_result = search(first1, last1,first2,last2); //查找
if(new_result == last1)
else{ //多次查找，查找到匹配的点return result;
result = new_result;
first1 = new_result;
++first1;
}
}
}
}
search，在序列一所涵盖的区间中，查找序列二的首次出现点,单纯的讲解方法不再考虑泛化。
char * search(char* first1, char* last1, char* first2, char* last2)
{
int len1 = last1 - first1; //字符串1长度
int len2 = last2 - first2; //字符串2长度
if(len2 > len1) return last1;
char* cur1 = first1; //当前字符
char* cur2 = first2; //当前字符
while(cur2 != last2){
if(*cur1 == *cur2){
cur1++;
cur2++;
}
else{
if(len1 == len2) return last1;
else{
cur1 = ++first;
cur2 = first2;
--len1;
}
}
}
return first1;
}
char* search_n(char* first, char *last, int count, int value)
{
if(count <= 0) return first;
else{
first = find(first, last, value);
while(first != last){
int n = count -1;
char* i = first;
++i;
while(i != last && n !=0 && *i == value){++i; --n;}
if(n == 0) return first;
else
first = find(i, last, value);
}
return last;
}
}