search原型：

std::search

template <class ForwardIterator1, class ForwardIterator2>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2);

template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>
   ForwardIterator1 search (ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2,
                            BinaryPredicate pred);

也就相当于一个子序列在一个序列中第一次出现的位置。

若匹配成功，返回[first1,last1)中匹配的第一个相应元素。

否则，返回last1.

行为类似于：

template<class ForwardIterator1, class ForwardIterator2>
  ForwardIterator1 search ( ForwardIterator1 first1, ForwardIterator1 last1,
                            ForwardIterator2 first2, ForwardIterator2 last2)
{
  if (first2==last2) return first1;  // specified in C++11
  
  while (first1!=last1)
  {
    ForwardIterator1 it1 = first1;
    ForwardIterator2 it2 = first2;
    while (*it1==*it2) {    // or: while (pred(*it1,*it2)) for version 2
        ++it1; ++it2;
        if (it2==last2) return first1;
        if (it1==last1) return last1;
    }
    ++first1;
  }
  return last1;
}

一个简单的例子：

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
void msearch(){
    char vc[]={"iamastudentstuden"};
    char vt[]={"student"};
    auto it=search(vc,vc+17,vt,vt+7);
    cout<<"auto it=search(vc,vc+17,vt,vt+7);;"<<endl;
    for(auto i=it;i!=vc+17;++i)
        cout<<*i;
    cout<<endl;
}

std::search_n

template <class ForwardIterator, class Size, class T>
   ForwardIterator search_n (ForwardIterator first, ForwardIterator last,
                             Size count, const T& val);

template <class ForwardIterator, class Size, class T, class BinaryPredicate>
   ForwardIterator search_n ( ForwardIterator first, ForwardIterator last,
                              Size count, const T& val, BinaryPredicate pred );

如果有，则返回第一次出现的首元素，否则返回last。

其行为类似于：

template<class ForwardIterator, class Size, class T>
  ForwardIterator search_n (ForwardIterator first, ForwardIterator last,
                            Size count, const T& val)
{
  ForwardIterator it, limit;
  Size i;

  limit=first; std::advance(limit,std::distance(first,last)-count);

  while (first!=limit)
  {
    it = first; i=0;
    while (*it==val)       // or: while (pred(*it,val)) for the pred version
      { ++it; if (++i==count) return first; }
    ++first;
  }
  return last;
}

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;
bool mypredicate (int i, int j) {
  return (i==j);
}
void msearchn(){
    int myints[]={10,20,30,30,20,10,10,20};
  std::vector<int> myvector (myints,myints+8);

  std::vector<int>::iterator it;

  // using default comparison:
  it = std::search_n (myvector.begin(), myvector.end(), 2, 30);

  if (it!=myvector.end())
    std::cout << "two 30s found at position " << (it-myvector.begin()) << '\n';
  else
    std::cout << "match not found\n";

  // using predicate comparison:
  it = std::search_n (myvector.begin(), myvector.end(), 2, 10, mypredicate);

  if (it!=myvector.end())
    std::cout << "two 10s found at position " << int(it-myvector.begin()) << '\n';
  else
    std::cout << "match not found\n";
}

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//写的错误或者不好的地方请多多指导，可以在下面留言或者点击左上方邮件地址给我发邮件，指出我的错误以及不足，以便我修改，更好的分享给大家，谢谢。

转载请注明出处：http://blog.csdn.net/qq844352155

author:天下无双

Email:coderguang@gmail.com

2014-9-26

于GDUT

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STL algorithm算法search，search_n（52）

原文：http://blog.csdn.net/qq844352155/article/details/39575787