C++ Algorithm sort()用法及代碼示例

C++算法sort()函數用於將[first, last)範圍內的元素按升序排序。

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

default (1)	
	template <class RandomAccessIterator>
  	void sort (RandomAccessIterator first, RandomAccessIterator last);

custom (2)	
	template <class RandomAccessIterator, class Compare>
  void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);

參數

first:一個隨機訪問迭代器，指向要排序的範圍中的第一個元素。

last:一個隨機訪問迭代器，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

排序複雜度的平均值是 N*log₂(N)，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。

注意：無效的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 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 << " ";
  });

  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 <iostream>     // std::cout
#include <algorithm>    // std::sort
#include <vector>       // std::vector

using namespace std;

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

struct myclass {
  bool operator() (int i,int j) { return (i<j);}
} myobject;

int main () {
  int myints[] = {32,71,12,45,26,80,53,33};
  vector<int> myvector (myints, myints+8);               // 32 71 12 45 26 80 53 33

  // using default comparison (operator <):
  sort (myvector.begin(), myvector.begin()+4);           //(12 32 45 71)26 80 53 33

  // using function as comp
  sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80)

  // using object as comp
  sort (myvector.begin(), myvector.end(), myobject);     //(12 26 32 33 45 53 71 80)

  // print out content:
  cout << "myvector contains:";
  for (vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
    cout << ' ' << *it;
  cout << '\n';

  return 0;
}

輸出：

myvector contains:12 26 32 33 45 53 71 80

例子3

讓我們看另一個簡單的例子：

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

using namespace std;
 
void print(const vector <std::string>& v)
{
    vector <string>::const_iterator i;
    for(i = v.begin(); i != v.end(); i++)
    {
        cout << *i << "    ";
    }
    cout << endl;
}
 
int main()
{
    vector <string> v;
    // Push functional programming languages
    v.push_back("Lisp");
    v.push_back("C#");
    v.push_back("Java");
    v.push_back("Python");
    v.push_back("C++");
    v.push_back("Pascal");
    v.push_back("Sql");
 
    // sort without predicate
    sort(v.begin(), v.end());
    cout << "Sorted list of functional programming languages - " << endl;
    print(v);
    // sort with predicate
    sort(v.begin(), v.end(), std::greater<std::string>());
    cout << "Reverse Sorted list of functional programming languages - " << endl;
    print(v);
}

輸出：

Sorted list of functional programming languages - 
C#    C++    Java    Lisp    Pascal    Python    Sql    
Reverse Sorted list of functional programming languages - 
Sql    Python    Pascal    Lisp    Java    C++    C#

示例 4

讓我們看另一個簡單的例子：

#include <vector>
#include <algorithm>
#include <functional>     
#include <iostream>
 
using namespace std;
 
// return whether first element is greater than the second
bool userdefgreater(int elem1, int elem2)
{    return elem1 > elem2;    }
 
int main()
{
  vector <int> vec1;  // container
  vector <int>::iterator Iter1;  // iterator
  int k;
  for (k = 0; k <= 15; k++)
    vec1.push_back(k);
  random_shuffle(vec1.begin(), vec1.end());
  cout <<"Original random shuffle vector vec1 data:\n";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
  sort(vec1.begin(), vec1.end());
  cout <<"\nSorted vector vec1 data:\n";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
  // to sort in descending order, specify binary predicate
  sort(vec1.begin(), vec1.end(), greater<int>());
  cout <<"\nRe sorted (greater) vector vec1 data:\n";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;
  // a user-defined binary predicate can also be used
  sort(vec1.begin(), vec1.end(), userdefgreater);
  cout <<"\nUser defined re sorted vector vec1 data:\n";
  for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
    cout <<*Iter1<<" ";
  cout <<endl;

  return 0;
}

輸出：

Original random shuffle vector vec1 data:
4 10 11 15 14 5 13 1 6 9 3 7 8 2 0 12 

Sorted vector vec1 data:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 

Re sorted (greater) vector vec1 data:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 

User defined re sorted vector vec1 data:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

相關用法

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