C++ Algorithm stable_sort()用法及代碼示例

C++ 算法 stable_sort() 函數用於將 [first, last) 範圍內的元素按升序排序，與 sort 類似，但保持等價元素的順序。

第一個版本使用運算符比較元素，第二個版本使用 comp 進行比較。

用法

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

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

參數

first: 一個雙向迭代器，指向要排序的範圍內的第一個元素。

last:一個雙向迭代器，指向要排序的範圍中過去的最後一個元素。

comp: 一個用戶定義的二元謂詞函數，它接受兩個參數，如果兩個參數按順序返回真，否則返回假。它遵循嚴格的弱排序來對元素進行排序。

返回值

空

複雜度

運行時複雜度取決於可用內存量。

如果有足夠的額外內存可用，那麽複雜性在 first 和 last 之間的距離上是線性的。最多執行 N*log₂(N) 元素比較，其中 N = last - first。

如果沒有額外的內存可用，那麽複雜性在 first 和 last 之間的距離上是多線性的。最多執行 N*log₂²(N) 元素比較，其中 N = last - first。

數據競爭

範圍 [first, last) 中的對象被修改。

異常

如果任何元素比較、元素交換或迭代器上的操作引發異常，則此函數將引發異常。

請注意，無效參數會導致未定義的行為。

例子1

讓我們看一個簡單的例子來演示 stable_sort() 的使用：

#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;
}

輸出：

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

例子2

讓我們看另一個簡單的例子：

#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;
}

輸出：

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

例子3

讓我們看另一個簡單的例子：

#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;
}

輸出：

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

示例 4

讓我們看另一個簡單的例子：

#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;
}

輸出：

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 )

相關用法

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