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C++ 算法中的 stable_sort函数

C++算法 stable_sort()函数用于将[first，last)参数内的元素按升序排序(例如sort)，但保持等效元素的顺序。

stable_sort - 语法

template <class RandomAccessIterator>
  void stable_sort ( RandomAccessIterator first, RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void stable_sort ( RandomAccessIterator first, RandomAccessIterator last,
                     Compare comp );

stable_sort - 参数

first:一个双向迭代器，指向要排序参数内的第一个元素。

last:一个双向迭代器，指向要排序参数内的最后一个最后一个元素。

comp :用户定义的二进制谓词函数，该函数接受两个参数，如果两个参数按顺序排列，则返回true，否则返回false。它遵循严格的弱排序来对元素进行排序。

stable_sort - 返回值

没有

stable_sort - 例子1

让我们看一个简单的示例来演示stable_sort()的用法:

在线运行复制代码

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  vector<int> v = {3, 1, 4, 2, 5};
  
    cout<<"Before sorting: ";
    for_each(v.begin(), v.end(), [](int x) {
    cout << x << " ";
  });

  stable_sort(v.begin(), v.end());
  
  cout<<"\nAfter sorting:  ";
  for_each(v.begin(), v.end(), [](int x) {
    cout << x << " ";
  });
  
  return 0;
}

输出:

Before sorting: 3 1 4 2 5 
After sorting:  1 2 3 4 5

stable_sort - 例子2

让我们看另一个简单的例子:

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在线运行复制代码

#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
 
using namespace std;
 
struct Employee {
    Employee(int age, string name) : age(age), name(name) { } 
    int age;
    string name; //Does not particpate in comparisons
};
 
bool operator<(const Employee &lhs, const Employee &rhs) {
    return lhs.age < rhs.age;
}
 
int main()
{
    vector<Employee> v = { 
        Employee(58, "Robin"),
        Employee(23, "Bob"),
        Employee(60, "Devid"),
    };  
 
    stable_sort(v.begin(), v.end());
    
    cout<<"Age : Name "<<endl<<"-----------\n";
    for (const Employee &e : v) {
        cout << e.age << " : " << e.name << '\n';
    }
    
    return 0;
}

输出:

Age : Name 
-----------
23 : Bob
58 : Robin
60 : Devid

stable_sort - 例子3

让我们看另一个简单的例子:

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在线运行复制代码

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>

using namespace std;
 
struct Student {
    string name;
    int sec;
    char group;
};
 
bool compBySec(Student a, Student b)
{
    return a.sec < b.sec;
}
 
bool compByGroup(Student a, Student b)
{
    return a.group < b.group;
}
 
bool compByName(Student a, Student b)
{
    return a.name < b.name;
}
 
void print(const vector <Student>& v)
{
    cout << "Name  \tSec\tGroup" << "\n-------------------------"<<endl;
    for (unsigned int i = 0; i < v.size(); i++)
    {   
        cout << v[i].name << "\t" << v[i].sec<< "\t"
                  << v[i].group << endl;
    }
}
 
int main()
{
    vector <Student> Students;
    string name[] = {"Anjali", "Bob", "Chinu  ", "Faizal ",
                          "Nikita ", "Deep ", "Aman", "Rohit "};
    int sec[] = {3, 4, 3, 3, 1, 4, 3, 2};
    int group[] = {'A', 'C', 'A', 'A', 'A', 'B', 'B', 'A'};
 
    for (int i = 0; i < 8; i++)
    {
        Student p;   
        p.name =  name[i];
        p.sec = sec[i];
        p.group = group[i];
        Students.push_back(p);
    }
    stable_sort(Students.begin(), Students.end(), compByName);
    cout << "Stable Sort by name" << endl;
    print(Students);
    cout << endl;
    stable_sort(Students.begin(), Students.end(), compBySec);
    cout << "Stable Sort by section" << endl;
    print(Students);
    
    return 0;
}

输出:

Stable Sort by name
Name  	Sec	Group
-------------------------
Aman	3	B
Anjali	3	A
Bob	4	C
Chinu  	3	A
Deep 	4	B
Faizal 	3	A
Nikita 	1	A
Rohit 	2	A

Stable Sort by section
Name  	Sec	Group
-------------------------
Nikita 	1	A
Rohit 	2	A
Aman	3	B
Anjali	3	A
Chinu  	3	A
Faizal 	3	A
Bob	4	C
Deep 	4	B

stable_sort - 例子4

让我们看另一个简单的例子:

在线运行复制代码

#include <vector>  
#include <algorithm>  
#include <functional>     //For greater<int>( )  
#include <iostream>  
  
// Return whether first element is greater than the second  
bool UDgreater (int elem1, int elem2 )  
{  
   return elem1 > elem2;  
}  
  
int main( )  
{  
   using namespace std;  
   vector <int> v1;  
   vector <int>::iterator Iter1;  
  
   int i;  
   for ( i = 0 ; i <= 5 ; i++ )  
   {  
      v1.push_back( 2 * i );  
   }  
  
   for ( i = 0 ; i <= 5 ; i++ )  
   {  
      v1.push_back( 2 * i  );  
   }  
  
   cout << "Original vector v1 = ( " ;  
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )  
      cout << *Iter1 << " ";  
   cout << ")" << endl;  
  
   stable_sort(v1.begin( ), v1.end( ) );  
   cout << "Sorted vector v1 = ( " ;  
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )  
      cout << *Iter1 << " ";  
   cout << ")" << endl;  
  
  //To sort in descending order, specify binary predicate  
   stable_sort(v1.begin( ), v1.end( ), greater<int>( ) );  
   cout << "Resorted (greater) vector v1 = ( " ;  
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )  
      cout << *Iter1 << " ";  
   cout << ")" << endl;  
  
  //A user-defined (UD) binary predicate can also be used  
   stable_sort(v1.begin( ), v1.end( ), UDgreater );  
   cout << "Resorted (UDgreater) vector v1 = ( " ;  
   for ( Iter1 = v1.begin( ) ; Iter1 != v1.end( ) ; Iter1++ )  
      cout << *Iter1 << " ";  
   cout << ")" << endl;  
   
   return 0;
}

输出:

Original vector v1 = ( 0 2 4 6 8 10 0 2 4 6 8 10 )
Sorted vector v1 = ( 0 0 2 2 4 4 6 6 8 8 10 10 )
Resorted (greater) vector v1 = ( 10 10 8 8 6 6 4 4 2 2 0 0 )
Resorted (UDgreater) vector v1 = ( 10 10 8 8 6 6 4 4 2 2 0 0 )

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