adjacent_find 源码剖析

一：用法解析

函数原型：

equality (1)    
template <class ForwardIterator>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last);
predicate (2)   
template <class ForwardIterator, class BinaryPredicate>
   ForwardIterator adjacent_find (ForwardIterator first, ForwardIterator last,
                                  BinaryPredicate pred);

功能：

在区间[ first ,last )找到第一组邻近相等（或者可使pred为真）的元素，返回该组的第一个元素的迭代器，如果找不到last。

例子：

// adjacent_find example
#include <iostream>     // std::cout
#include <algorithm>    // std::adjacent_find
#include <vector>       // std::vector

bool myfunction (int i, int j) {
  return (i==j);
}

int main () {
  int myints[] = {5,20,5,30,30,20,10,10,20};
  std::vector<int> myvector (myints,myints+8);
  std::vector<int>::iterator it;

  // using default comparison:
  it = std::adjacent_find (myvector.begin(), myvector.end());

  if (it!=myvector.end())
    std::cout << "the first pair of repeated elements are: " << *it << '\n';

  //using predicate comparison:
  it = std::adjacent_find (++it, myvector.end(), myfunction);

  if (it!=myvector.end())
    std::cout << "the second pair of repeated elements are: " << *it << '\n';

  return 0;
}

运行如下：

the first pair of repeated elements are: 30
the second pair of repeated elements are: 10

二：源码剖析

// TEMPLATE FUNCTION adjacent_find WITH PRED
template<class _FwdIt,
  class _Pr> inline
  _FwdIt _Adjacent_find(_FwdIt _First, _FwdIt _Last, _Pr _Pred)
  { // find first satisfying _Pred with successor
  if (_First != _Last)
    for (_FwdIt _Firstb; (void)(_Firstb = _First), ++_First != _Last; )
      if (_Pred(*_Firstb, *_First))
        return (_Firstb);
  return (_Last);
  }

template<class _FwdIt,
  class _Pr> inline
  _FwdIt adjacent_find(_FwdIt _First, _FwdIt _Last, _Pr _Pred)
  { // find first satisfying _Pred with successor
  _DEBUG_RANGE(_First, _Last);
  _DEBUG_POINTER_IF(_First != _Last && _STD next(_First) != _Last, _Pred);
  return (_Rechecked(_First,
    _Adjacent_find(_Unchecked(_First), _Unchecked(_Last), _Pred)));
  }

    // TEMPLATE FUNCTION adjacent_find
template<class _FwdIt> inline
  _FwdIt adjacent_find(_FwdIt _First, _FwdIt _Last)
  { // find first matching successor
  return (_STD adjacent_find(_First, _Last, equal_to<>()));
  }

源码摘抄自Visual Studio 2015安装目录algorithm文件中。

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