这里接着上篇进行总结。主要解析算法函数count、count_if、mismatch、equal、search、search_n以及find_end。给出算法函数的实现及測试用例。以下直接进入正题。

统计等于某值的容器元素个数count

count函数用于计算容器中某个给定值的出现次数。计算迭代区间[first,last)上等于val值的元素个数ret。返回计数。

//count算法函数的实现代码template 
      
         typename iterator_traits
       
        ::difference_type    count (InputIterator first, InputIterator last, const T& val){  typename iterator_traits
        
         ::difference_type  ret = 0;  while (first!=last)  {    if (*first == val)         ++ret;    ++first;  }  return ret;}
        
       
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;int main(void){    list
         
           l;    for(int i=0; i<100; i++)        l.push_back(i%20);    int num=0;    int value=9;    num=count(l.begin(), l.end(), value);    cout << "链表中元素等于value的元素个数为: "        << num << endl;      return 0;}
         
        
       
      

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条件统计容器元素个数count_if

与count算法函数相似，count_if算法函数仅仅是使用谓词推断pred，统计迭代器区间[first,last)上满足条件的元素个数n，返回计数。

//count_if算法函数代码template 
      
         typename iterator_traits
       
        ::difference_type    count_if (InputIterator first, InputIterator last, UnaryPredicate pred){  typename iterator_traits
        
         ::difference_type n = 0;  while (first!=last) {    if (pred(*first)) ++n;    ++first;  }  return n;}
        
       
      

//測试用例#include 
      
            #include 
       
           #include 
        
               using namespace std;//是否为奇数bool IsOdd (int i) {     return ((i%2)==1); }int main (){    vector
         
           v;    for (int i=1; i<10; i++)         v.push_back(i);     int mycount = count_if (v.begin(), v.end(), IsOdd);    cout << "v容器包括 " << mycount  << " 奇数值。
         
        
       
      

\n"

; return 0; }

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元素不匹配查找mismatch

mismatch算法函数比較两个序列，找出首个不匹配元素的位置。

找出迭代区间[first1,last1)上第一个元素i，他与迭代区间[first2,first2+(last1-first1))上的元素（first2+(i-first1))不相等（或不满足二元谓词pred条件）。通过pair返回这两个元素的迭代器。指示不匹配元素 的位置。

)   template 
      
         pair
       
            mismatch (InputIterator1 first1, InputIterator1 last1,              InputIterator2 first2);template 
        
           pair
         
              mismatch (InputIterator1 first1, InputIterator1 last1,              InputIterator2 first2, BinaryPredicate pred);
         
        
       
      

• mismatch函数的模板类型选择了不同的符号InputIterator1和InputIterator2，表示可取不同的容器迭代器。

//mismatch算法函数的代码template 
      
         pair
       
            mismatch (InputIterator1 first1, InputIterator1 last1, InputIterator2 first2 ){  while ( (first1!=last1) && (*first1==*first2) )  // or: pred(*first1,*first2), for version 2  { ++first1; ++first2; }  return std::make_pair(first1,first2);}
       
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;bool strEqual(const char* s1, const char* s2){    return strcmp(s1, s2) == 0 ?
        
       
      

1 : 0; } int main(void) { //初始化向量v1、v2 vector<int> v1, v2; v1.push_back(2); v1.push_back(0); v1.push_back(0); v1.push_back(6); v2.push_back(2); v2.push_back(0); v2.push_back(0); v2.push_back(7); //v1和v2不匹配检查 pair<vector<int>::iterator, vector<int>::iterator> result1= mismatch(v1.begin(), v1.end(), v2.begin()); if(result1.first == v1.end() && result1.second == v1.end()) cout << "v1和v2全然同样" << endl; else cout << "v1和v2不同样,不匹配的数是:\n" << *result1.first << endl << *result1.second << endl << endl; //初始化字符串s1、s2 char* s1[] = {

"apple", "pear", "watermelon", "banana", "grape"}; char* s2[] = {

"apple", "pears", "watermelons", "banana", "grape"}; //s1和s2不匹配检查 pair<char**, char**> result2=mismatch(s1, s1+5, s2, strEqual); if(result2.first == s1+5 && result2.second ==s2+5) cout << "s1和s2全然同样" << endl; else cout << "s1与s2不同样,不匹配的字符串为:\n" << s1[result2.first -s1] << endl << s2[result2.second -s2] << endl << endl; return 0; }

---

元素相等推断equal

相似mismatch、equal算法函数也是逐一比較两个序列的元素是否相等，仅仅是equal函数返回true/false，不返回迭代器值。也是有例如以下两种使用原型。假设迭代区间[first1,last1)和迭代器区间[first2,first2+(last1-first1))上的元素相等（或满足二元谓词推断条件pred),返回true，否则返回false。

template 
      
         bool equal (InputIterator1 first1, InputIterator1 last1,              InputIterator2 first2);template 
       
          bool equal (InputIterator1 first1, InputIterator1 last1,              InputIterator2 first2, BinaryPredicate pred);
       
      

//equal算法函数的代码template 
      
         bool equal ( InputIterator1 first1, InputIterator1 last1, InputIterator2 first2 ){  while (first1!=last1) {    if (!(*first1 == *first2))   // or: if (!pred(*first1,*first2)), for version 2      return false;    ++first1; ++first2;  }  return true;}
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;bool absEqual(int a, int b){    return (a== abs(b) || abs(a) == b) ? 1:0;}int main(void){    //初始化向量v1、v2    vector 
         
           v1(5);    vector 
          
            v2(5);    for(unsigned int i = 0; i < v1.size(); i++) {        v1[i] = i;        v2[i] = -1 * i;    }    //v1、v2相等检查    if(equal(v1.begin(), v1.end(), v2.begin(), absEqual))        cout << "v1和v2元素的绝对值全然相等" << endl;    else        cout << "v1和v2元素的绝对值不全然相等" << endl;    return 0;}
          
         
        
       
      

---

子序列搜索search

search算法函数在一个序列中搜索与还有一个序列匹配的子序列。有例如以下两个原型。在迭代器区间[first1,last1)上找出与迭代器区间[first2,last2)全然匹配（或满足二元谓词推断pred）的子序列，返回子序列首个元素的迭代器值，或返回last1表示没有匹配的子序列。

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

//search算法函数的代码template
      
         ForwardIterator1 search ( ForwardIterator1 first1, ForwardIterator1 last1,                            ForwardIterator2 first2, ForwardIterator2 last2){  if (first2==last2) return first1;    while (first1!=last1)  {    ForwardIterator1 it1 = first1;    ForwardIterator2 it2 = first2;     // or: while (pred(*it1,*it2)) for version 2    while (*it1==*it2) {           ++it1; ++it2;        if (it2==last2) return first1;        if (it1==last1) return last1;    }    ++first1;  }  return last1;}
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;int main(void){    //初始化向量v1={5, 6, 7, 8, 9 }     vector
         
           v1;     v1.push_back(5);    v1.push_back(6);    v1.push_back(7);    v1.push_back(8);    v1.push_back(9);    //初始化向量v2={7, 8}    vector
          
            v2;    v2.push_back(7);    v2.push_back(8);    //检查v2是否构成v1的子序列    vector
           
            ::iterator iterLocation; iterLocation=search(v1.begin(), v1.end(), v2.begin(), v2.end()); //打印从v1[2]開始匹配 if(iterLocation != v1.end()) cout << "v2的元素包括在v1中,起始元素为" << "v1[" << iterLocation - v1.begin() << "]\n"; else cout << "v2的元素不包括在v1中" << endl; return 0;}
           
          
         
        
       
      

---

反复元素子序列搜索search_n

search_n算法函数搜索序列中是否有一系列元素值均为某个给定值的子序列。

有例如以下两个原型。分别在迭代器区间[first,last)上搜索是否有count个连续元素，其值均等于value（或满足谓词推断pred的条件）。返回子序列首元素的迭代器，或返回last表示没有反复元素的子序列。

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

//search_n算法函数的代码template
      
         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;}
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;int main(void){    vector
         
           v;    v.push_back(1);    v.push_back(8);    v.push_back(6);    v.push_back(6);    v.push_back(9);    vector
          
           ::iterator iLocation;    iLocation=search_n(v.begin(), v.end(), 2, 6);    if(iLocation != v.end())        cout << "在v中找到2个连续的元素6" << endl;    else         cout << "v中没有2个连续的元素6" << endl;    return 0;}
          
         
        
       
      

---

最后一个子序列搜索find_end

find_end算法函数在一个序列中搜索出最后一个与还有一序列匹配的子序列。有例如以下两个使用原型。

在迭代器区间[first1,last1)中搜索出与迭代器区间[first2,last2)元素匹配的子序列。返回首元素的迭代器或返回last1，表示没有子序列匹配。

template 
      
          ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,                              ForwardIterator2 first2, ForwardIterator2 last2);template 
       
           ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,                              ForwardIterator2 first2, ForwardIterator2 last2,                              BinaryPredicate pred);
       
      

//find_end函数实现template
      
         ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,                             ForwardIterator2 first2, ForwardIterator2 last2){  if (first2==last2) return last1;  // specified in C++11  ForwardIterator1 ret = last1;  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) { ret=first1; break; }        if (it1==last1) return ret;    }    ++first1;  }  return ret;}
      

//測试用例#include 
      
       #include 
       
        #include 
        
         using namespace std;int main(void){       //初始化向量v1={-5, 1, 2, -6, -8, 1, 2, -11}    vector
         
           v1;    v1.push_back(-5);    v1.push_back(1);    v1.push_back(2);    v1.push_back(-6);    v1.push_back(-8);    v1.push_back(1);    v1.push_back(2);    v1.push_back(-11);    //初始化向量v2={1, 2}    vector
          
            v2;    v2.push_back(1);    v2.push_back(2);    //v1中查找最后一个子序列v2    vector
           
            ::iterator iLocation; iLocation=find_end(v1.begin(), v1.end(), v2.begin(), v2.end()); //打印子序列在v1的起始位置v[5] if(iLocation != v1.end()) cout << "v1中找到最后一个匹配v2的子序列,位置在" << "v1[" << iLocation - v1.begin() << "]" << endl; return 0;}
           
          
         
        
       
      

---

完结。

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