C++ STL（18）：排序算法

#include <iostream>
#include <algorithm>
#include <functional> //for greater
#include <iterator>
#include <vector>
#include <math.h>
#include <assert.h>
 
class Job
{
public:
     enum Priority_code{ standard, normal, high };
     Job(int i, Priority_code pc = standard)
              : id(i), pri(pc){ }
     
     Priority_code getPri() const { return pri; }
     int getId() const { return id; }
 
     friend std::ostream& operator<<(std::ostream& os, const Job& job)
     {
          os << job.getId() << "(" << job.getPri() << ")";
          return os;
     }
 
     friend bool operator<(const Job& job1, const Job& job2)
     {
          return job1.getPri() > job2.getPri();
     }
 
public:
     Priority_code pri;
     int id;
};
 
//排序算法
int main()
{
     /************************************************************************/
     //sort
     /************************************************************************/
     /*
          sort:以非递减的顺序进行排序，
          sort是个不稳定的排序算法，假设[first,last)中存在两个相等的元素，sort排完序之后不能保证这两个元素的相对位置还和原来一样
          版本1：使用operator<来比较，必导致is_sorted(first,last)为true
          版本2：采用function object comp来比较，必导致is_sorted(first,last,comp)为true
     */
     /*
     template<class RandomAccessIterator>
     void sort(
          RandomAccessIterator _First,
          RandomAccessIterator _Last
          );
     template<class RandomAccessIterator, class Pr>
     void sort(
          RandomAccessIterator _First,
          RandomAccessIterator _Last,
          BinaryPredicate _Comp
      );
     */
     int A[] = { 1, 4, 8, 2, 6, 5, 7 };
     std::sort(std::begin(A), std::end(A));
     assert(std::is_sorted(std::begin(A), std::end(A)));
     //1 2 4 5 6 7 8
     std::for_each(std::begin(A), std::end(A), [](const int i){std::cout << i << " "; });
     std::cout << std::endl;
 
     int B[] = { 1, 4, 8, 2, 6, 5, 7 };
     std::sort(std::begin(B), std::end(B), std::greater<int>());
     assert(std::is_sorted(std::begin(B), std::end(B), std::greater<int>()));
     //8 7 6 5 4 2 1
     std::for_each(std::begin(B), std::end(B), [](const int i){std::cout << i << " "; });
     std::cout << std::endl;
 
     int C[] = { 1, -4, 8, -2, -6, 5, 7 };
     std::sort(std::begin(C), std::end(C),[](const int v1, const int v2)
     {
          return abs(v1) > abs(v2);
     });
     //8 7 -6 5 -4 -2 1
     std::for_each(std::begin(C), std::end(C), [](const int i){std::cout << i << " "; });
     std::cout << std::endl;

     /************************************************************************/
     //stable_sort
     /************************************************************************/
     //stable_sort:与sort类似，但是stable_sort是个稳定的排序算法，即能保证两个相等的元素在排完序之后相对位置保持不变
     /*
     template<class BidirectionalIterator>
     void stable_sort(
          BidirectionalIterator _First,
          BidirectionalIterator _Last
      );
     template<class BidirectionalIterator, class BinaryPredicate>
     void stable_sort(
          BidirectionalIterator _First,
          BidirectionalIterator _Last,
          BinaryPredicate _Comp
      );
     */
     char s[] = "fdBeACFDbEac";
     std::stable_sort(s, s + 12,[](const char c1, const char c2)
     {
          return tolower(c1) < tolower(c2);
     });
     std::cout << s << std::endl; //AaBbCcdDeEfF
     std::cout << "==============================" << std::endl;
 
     std::vector<Job> jobs;
     jobs.push_back(Job(1, Job::normal));
     jobs.push_back(Job(2, Job::standard));
     jobs.push_back(Job(3, Job::normal));
     jobs.push_back(Job(4, Job::high));
     jobs.push_back(Job(5));
     jobs.push_back(Job(6, Job::high));
     std::stable_sort(jobs.begin(), jobs.end());
     std::copy(jobs.begin(), jobs.end(), std::ostream_iterator<Job>(std::cout, "\n"));

     std::cout << "==============================" << std::endl;
     /************************************************************************/
     //partial_sort
     /************************************************************************/
     /*
          partial_sort:重新排列[first,last)，使得[first,sortEnd)按照递增顺序排列，其余的可以不按照特定顺序排列，如果_SortEnd==_First，即不做任何的排序；如果_SortEnd==_Last，即把整个[first,last)进行排序
      */
     /*
     template<class RandomAccessIterator>
     void partial_sort(
          RandomAccessIterator _First,
          RandomAccessIterator _SortEnd,
          RandomAccessIterator _Last
      );
     template<class RandomAccessIterator, class BinaryPredicate>
     void partial_sort(
          RandomAccessIterator _First,
          RandomAccessIterator _SortEnd,
          RandomAccessIterator _Last
          BinaryPredicate _Comp
      );
     */
     //试找寻数组中前5个最小值，及A[0]~A[4]以非递减的顺序排序，其余不保证顺序
     int AA[] = { 7, 2, 6, 11, 9, 3, 12, 10, 8, 4, 1, 5 };
     int *p = std::begin(AA);
     std::advance(p, 5);
     std::partial_sort(std::begin(AA), p, std::end(AA));
     //1 2 3 4 5 11 12 10 9 8 7 6
     std::copy(std::begin(AA), std::end(AA), std::ostream_iterator<int>(std::cout, " "));
     std::cout << std::endl;
 
 
     /************************************************************************/
     //partial_sort_copy
     /************************************************************************/
     /*
          partial_sort_copy:函数会从[first1,last1)内复制N个最小元素到[first2,last2)之中，
          这里的N是last1-first1和last2-first2两者中的最小值，被复制过去的元素以递增顺序排列
      */
     /*
     template<class InputIterator, class RandomAccessIterator>
     RandomAccessIterator partial_sort_copy(
          InputIterator _First1,
          InputIterator _Last1,
          RandomAccessIterator _First2,
          RandomAccessIterator _Last2
      );
     template<class InputIterator, class RandomAccessIterator, class BinaryPredicate>
     RandomAccessIterator partial_sort_copy(
      InputIterator _First1,
          InputIterator _Last1,
          RandomAccessIterator _First2,
          RandomAccessIterator _Last2,
          BinaryPredicate _Comp
      );
     */
     //将数组BB中的前4个最小值复制到一个vector中去
     int BB[] = { 7, 2, 6, 11, 9, 3, 12, 10, 8, 4, 1, 5 };
     std::vector<int> iv(4);
     std::partial_sort_copy(std::begin(BB), std::end(BB),iv.begin(), iv.end());
     //1 2 3 4
     std::copy(iv.begin(), iv.end(), std::ostream_iterator<int>(std::cout, " "));
     std::cout << std::endl;
 
 
     /************************************************************************/
     //nth_element
     /************************************************************************/
     /*
          nth_element:函数重新排列[first,last)，使得iterator _Nth所指元素与整个[first,last)排序后的同一位置的元素相同，此外，也保证了[nth,last)内的任意元素都大于[first,nth)内的任意元素，而并不保证[first,nth)与[nth,last)内的元素保持一种顺序
      */
     /*
     template<class RandomAccessIterator>
     void nth_element(
          RandomAccessIterator _First,
          RandomAccessIterator _Nth,
          RandomAccessIterator _Last
      );
     template<class RandomAccessIterator, class BinaryPredicate>
     void nth_element(
          RandomAccessIterator _First,
          RandomAccessIterator _Nth,
          RandomAccessIterator _Last,
          BinaryPredicate _Comp
      );
     */
     int CC[] = { 7, 2, 6, 11, 9, 3, 12, 10, 8, 4, 1, 5 };
     int *pp = std::begin(CC);
     std::advance(pp, 4);
     std::nth_element(std::begin(CC), pp, std::end(CC));
     //?????
     std::copy(std::begin(CC), std::end(CC), std::ostream_iterator<int>(std::cout, " "));
     std::cout << std::endl;


     /************************************************************************/
     //is_sorted
     /************************************************************************/
     //is_sorted:用来测试某个序列是否已经排好序，已排好返回true，反之返回false
     /*
     template <class ForwardIterator>
     bool is_sorted(
          ForwardIterator _First,
          ForwardIterator _Last
      );
  
     template <class ForwardIterator, class StrictWeakOrdering>
     bool is_sorted(
          ForwardIterator _First,
          ForwardIterator _Last,
          StrictWeakOrdering _Comp
      );
     */
     //略 
     return 0;
}

运算结果：
1 2 4 5 6 7 8
8 7 6 5 4 2 1
8 7 -6 5 -4 -2 1
AaBbCcdDeEfF
===========================
4(2)
6(2)
1(1)
3(1)
2(0)
5(0)
===========================
1 2 3 4 5 11 12 10 9 8 7 6
1 2 3 4
1 2 3 4 5 6 7 8 9 10 11 12 

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