stl非变易算法（二）

这里接着上篇stl非变易算法（一）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测试用例。下面直接进入正题。

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 <class InputIterator, class T>  typename iterator_traits<InputIterator>::difference_type    count (InputIterator first, InputIterator last, const T& val){  typename iterator_traits<InputIterator>::difference_type  ret = 0;  while (first!=last)  {    if (*first == val)         ++ret;    ++first;  }  return ret;}

//测试用例#include <algorithm>#include <list>#include <iostream>using namespace std;int main(void){    list<int> 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算法函数类似，count_if算法函数只是使用谓词判断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 <class InputIterator, class UnaryPredicate>  typename iterator_traits<InputIterator>::difference_type    count_if (InputIterator first, InputIterator last, UnaryPredicate pred){  typename iterator_traits<InputIterator>::difference_type n = 0;  while (first!=last) {    if (pred(*first)) ++n;    ++first;  }  return n;}

//测试用例#include <iostream>     #include <algorithm>   #include <vector>      using namespace std;//是否为奇数bool IsOdd (int i) {     return ((i%2)==1); }int main (){    vector<int> v;    for (int i=1; i<10; i++)         v.push_back(i);     int mycount = count_if (v.begin(), v.end(), IsOdd);    cout << "v容器包含 " << mycount  << " 奇数值。\n";    return 0;}

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元素不匹配查找mismatch

mismatch算法函数比较两个序列，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 <class InputIterator1, class InputIterator2>  pair<InputIterator1, InputIterator2>    mismatch (InputIterator1 first1, InputIterator1 last1,              InputIterator2 first2);template <class InputIterator1, class InputIterator2, class BinaryPredicate>  pair<InputIterator1, InputIterator2>    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 <class InputIterator1, class InputIterator2>  pair<InputIterator1, InputIterator2>    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);}       

//测试用例#include <algorithm>#include <vector>#include <iostream>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完全相同" << endl;    else        cout << "v1和v2不相同,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完全相同" << endl;    else        cout << "s1与s2不相同,不匹配的字符串为:\n"         << s1[result2.first -s1] << endl        << s2[result2.second -s2] << endl << endl;    return 0;}

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元素相等判断equal

类似mismatch、equal算法函数也是逐一比较两个序列的元素是否相等，只是equal函数返回true/false，不返回迭代器值。也是有如下两种使用原型。如果迭代区间[first1,last1)和迭代器区间[first2,first2+(last1-first1))上的元素相等（或满足二元谓词判断条件pred),返回true，否则返回false。

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

//equal算法函数的代码template <class InputIterator1, class InputIterator2>  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;}

//测试用例#include <algorithm>#include <vector>#include <iostream>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 <int> v1(5);    vector <int> 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元素的绝对值完全相等" << endl;    else        cout << "v1和v2元素的绝对值不完全相等" << endl;    return 0;}

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子序列搜索search

search算法函数在一个序列中搜索与另一个序列匹配的子序列。有如下两个原型。在迭代器区间[first1,last1)上找出与迭代器区间[first2,last2)完全匹配（或满足二元谓词判断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 <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);

//search算法函数的代码template<class ForwardIterator1, class ForwardIterator2>  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;}     

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

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重复元素子序列搜索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。有如下两个原型。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（或满足谓词判断pred的条件），返回子序列首元素的迭代器，或返回last表示没有重复元素的子序列。

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 );    

//search_n算法函数的代码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;} 

//测试用例#include <algorithm>#include <vector>#include <iostream>using namespace std;int main(void){    vector<int> v;    v.push_back(1);    v.push_back(8);    v.push_back(6);    v.push_back(6);    v.push_back(9);    vector<int>::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;}       

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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另一序列匹配的子序列。有如下两个使用原型。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 <class ForwardIterator1, class ForwardIterator2>   ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,                              ForwardIterator2 first2, ForwardIterator2 last2);template <class ForwardIterator1, class ForwardIterator2, class BinaryPredicate>   ForwardIterator1 find_end (ForwardIterator1 first1, ForwardIterator1 last1,                              ForwardIterator2 first2, ForwardIterator2 last2,                              BinaryPredicate pred);          

//find_end函数实现template<class ForwardIterator1, class ForwardIterator2>  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;}

//测试用例#include <algorithm>#include <vector>#include <iostream>using namespace std;int main(void){       //初始化向量v1={-5, 1, 2, -6, -8, 1, 2, -11}    vector<int> 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<int> v2;    v2.push_back(1);    v2.push_back(2);    //v1中查找最后一个子序列v2    vector<int>::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;}     

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完结。
转载请注明出处：http://blog.csdn.net/lsh_2013/article/details/46849279