代码合集（1）——容器算法之合并 merge

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本文介绍了C++标准库中的排序算法及集合操作函数，包括merge、inplace_merge等用于合并排序的功能，以及includes、set_union等用于集合运算的操作。通过示例展示了如何使用这些函数对序列进行操作。

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1、merge：将两个序列合并成一个新的序列，并对新的序列排序
原型：
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator merge ( InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,OutputIterator result );
template <class InputIterator1, class InputIterator2,class OutputIterator, class Compare>
OutputIterator merge ( InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,OutputIterator result, Compare comp );
示例：

// merge algorithm example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);
  vector<int>::iterator it;

  sort (first,first+5);
  sort (second,second+5);
  merge (first,first+5,second,second+5,v.begin());

  cout << "The resulting vector contains:";
  for (it=v.begin(); it!=v.end(); ++it)
    cout << " " << *it;

  cout << endl;

  return 0;
}

2、inplace_merge：将两个序列合并成一个新的序列,并对新的序列进行归并排序(这两个序列必须要进过排序)
原型：
template <class BidirectionalIterator>
void inplace_merge ( BidirectionalIterator first, BidirectionalIterator middle,
BidirectionalIterator last );

template <class BidirectionalIterator, class Compare>
void inplace_merge ( BidirectionalIterator first, BidirectionalIterator middle,
BidirectionalIterator last, Compare comp );
示例:

// inplace_merge example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);
  vector<int>::iterator it;

  sort (first,first+5);
  sort (second,second+5);

  copy (first,first+5,v.begin());
  copy (second,second+5,v.begin()+5);

  inplace_merge (v.begin(),v.begin()+5,v.end());

  cout << "The resulting vector contains:";
  for (it=v.begin(); it!=v.end(); ++it)
    cout << " " << *it;

  cout << endl;

  return 0;
}

3、includes：测试是一个序列是否在另一个序列中
原型：
template <class InputIterator1, class InputIterator2>
bool includes ( InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2 );
template <class InputIterator1, class InputIterator2, class Compare>
bool includes ( InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2, Compare comp );
示例:

// includes algorithm example
#include <iostream>
#include <algorithm>
using namespace std;

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

int main () {
  int container[] = {5,10,15,20,25,30,35,40,45,50};
  int continent[] = {40,30,20,10};

  sort (container,container+10);
  sort (continent,continent+4);

  // using default comparison:
  if ( includes(container,container+10,continent,continent+4) )
    cout << "container includes continent!" << endl;

  // using myfunction as comp:
  if ( includes(container,container+10,continent,continent+4, myfunction) )
    cout << "container includes continent!" << endl;

  return 0;
}

4、set_union：和merge类似，不过新序列中没有重复的元素
原型：
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_union ( InputIterator1 first1, InputIterator1 last1,
                           InputIterator2 first2, InputIterator2 last2,OutputIterator result );
template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
OutputIterator set_union ( InputIterator1 first1, InputIterator1 last1,
                           InputIterator2 first2, InputIterator2 last2,OutputIterator result, Compare comp );
示例：

// set_union example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;

  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50

  it=set_union (first, first+5, second, second+5, v.begin());
                                               // 5 10 15 20 25 30 40 50  0  0

  cout << "union has " << int(it - v.begin()) << " elements.\n";

  return 0;
}

5、set_intersection：两个序列的交集
原型：
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
                                  InputIterator2 first2, InputIterator2 last2,OutputIterator result );
template <class InputIterator1, class InputIterator2,class OutputIterator, class Compare>
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
                                  InputIterator2 first2, InputIterator2 last2,OutputIterator result, Compare comp );
示例：

// set_intersection example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;

  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50

  it=set_intersection (first, first+5, second, second+5, v.begin());
                                               // 10 20 0  0  0  0  0  0  0  0

  cout << "intersection has " << int(it - v.begin()) << " elements.\n";

  return 0;
}

6、set_difference：序列(first1,last1)不在序列(first2,last2)中的元素
原型：
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
      InputIterator2 first2, InputIterator2 last2,outputIterator result );
template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
OutputIterator set_intersection ( InputIterator1 first1, InputIterator1 last1,
                                  InputIterator2 first2, InputIterator2 last2,OutputIterator result, Compare comp );
示例：

// set_difference example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;

  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50

  it=set_difference (first, first+5, second, second+5, v.begin());
                                               // 5 15 25  0  0  0  0  0  0  0

  cout << "difference has " << int(it - v.begin()) << " elements.\n";

  return 0;
}

7、set_symmetric_difference：所有不在序列(first1,last1)和序列(first2,last2)中的元素
原型：
template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator    set_symmetric_difference ( InputIterator1 first1, InputIterator1 last1,
                                             InputIterator2 first2, InputIterator2 last2,OutputIterator result );
template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
OutputIterator    set_symmetric_difference ( InputIterator1 first1, InputIterator1 last1,
                                             InputIterator2 first2, InputIterator2 last2,OutputIterator result, Compare comp );
示例：

// set_symmetric_difference example
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main () {
  int first[] = {5,10,15,20,25};
  int second[] = {50,40,30,20,10};
  vector<int> v(10);                           // 0  0  0  0  0  0  0  0  0  0
  vector<int>::iterator it;

  sort (first,first+5);     //  5 10 15 20 25
  sort (second,second+5);   // 10 20 30 40 50

  it=set_symmetric_difference (first, first+5, second, second+5, v.begin());
                                               // 5 15 25 30 40 50  0  0  0  0

  cout << "symmetric difference has " << int(it - v.begin()) << " elements.\n";

  return 0;
}