STL学习（自学手册+源码分析）之算法源码代码剖析（11个例子）

1.1 accumulate（两个版本）

1.2 for_each

template <class InputIterator, class Function>
Function for_each(InputIterator first, InputIterator last, Function f) {
  for ( ; first != last; ++first)
    f(*first);//用可调用对象f来遍历操作
  return f;
}

1.3 replace相关

template <class ForwardIterator, class T>
void replace(ForwardIterator first, ForwardIterator last, const T& old_value,
             const T& new_value) {
  for ( ; first != last; ++first)
    if (*first == old_value) *first = new_value;
}
//范围内所有的oldValue都被newValue取代

template <class ForwardIterator, class Predicate, class T>
void replace_if(ForwardIterator first, ForwardIterator last, Predicate pred,
                const T& new_value) {
  for ( ; first != last; ++first)
    if (pred(*first)) *first = new_value;
}
//pred要利用相关的条件来做过滤

template <class InputIterator, class OutputIterator, class T>
OutputIterator replace_copy(InputIterator first, InputIterator last,
                            OutputIterator result, const T& old_value,
                            const T& new_value) {
  for ( ; first != last; ++first, ++result)
    *result = *first == old_value ? new_value : *first;
  return result;
}

1.4 count相关

template <class InputIterator, class T, class Size>
void count(InputIterator first, InputIterator last, const T& value,
           Size& n) {
  for ( ; first != last; ++first)//遍历
    if (*first == value)//如果和value相等
      ++n;//计数器累加1
}

template <class InputIterator, class Predicate, class Size>
void count_if(InputIterator first, InputIterator last, Predicate pred,
              Size& n) {
  for ( ; first != last; ++first)
    if (pred(*first))
      ++n;
}
//pred是条件 符合条件再计数

有一些容器自带适合自己版本的count()，使用时应优先使用自带的。

1.5 find相关

template <class InputIterator, class T>
InputIterator find(InputIterator first, InputIterator last, const T& value) {
  while (first != last && *first != value) ++first;
  return first;
}

template <class InputIterator, class Predicate>
InputIterator find_if(InputIterator first, InputIterator last,
                      Predicate pred) {
  while (first != last && !pred(*first)) ++first;
  return first;
}

有些容器实现了自己版本的find()

1.6 binary search相关

template <class ForwardIterator, class T>
bool binary_search(ForwardIterator first, ForwardIterator last,
                   const T& value) {
  ForwardIterator i = lower_bound(first, last, value);
  return i != last && !(value < *i);
}

template <class ForwardIterator, class T, class Compare>
bool binary_search(ForwardIterator first, ForwardIterator last, const T& value,
                   Compare comp) {
  ForwardIterator i = lower_bound(first, last, value, comp);
  return i != last && !comp(value, *i);
}