排序“的std :: vector”的含类

Question

排序方式使用二进制谓词和std::sort

我需要为这个样本...

Answer 1

下面是一个使用两种不同类型谓词的示例的另一适配。指定的谓词可以是一个函数指针或一个函数，它是一个定义operator（）的类，以便实例化时的对象可以像函数一样使用。请注意，我必须在功能标题中再添加一个标题包含。这是因为函数继承自std库中定义的binary_function。

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

using namespace std; 

class MyData 
{ 
    public: 
    static bool compareMyDataPredicate(MyData lhs, MyData rhs) { return (lhs.m_iData <      rhs.m_iData); } 
    // declare the functor nested within MyData. 
     struct compareMyDataFunctor : public binary_function<MyData, MyData, bool> 
    { 
     bool operator()(MyData lhs, MyData rhs) 
     { 
      return (lhs.m_iData < rhs.m_iData); 
     } 
    }; 

    int m_iData; 
     string m_strSomeOtherData; 
    }; 


int main() 
{ 
    // Create a vector that contents elements of type MyData 
    vector<MyData> myvector; 

     // Add data to the vector 
     MyData data; 
     for(unsigned int i = 0; i < 10; ++i) 
     { 
      data.m_iData = i; 
      myvector.push_back(data); 
     } 

    // shuffle the elements randomly 
     std::random_shuffle(myvector.begin(), myvector.end()); 

     // Sort the vector using predicate and std::sort. In this case the predicate is  a static 
     // member function. 
     std::sort(myvector.begin(), myvector.end(), MyData::compareMyDataPredicate); 

     // Dump the vector to check the result 
    for (vector<MyData>::const_iterator citer = myvector.begin(); 
     citer != myvector.end(); ++citer) 
    { 
     cout << (*citer).m_iData << endl; 
    } 

    // Now shuffle and sort using a functor. It has the same effect but is just a different 
     // way of doing it which is more object oriented. 
     std::random_shuffle(myvector.begin(), myvector.end()); 

     // Sort the vector using predicate and std::sort. In this case the predicate is a functor. 
     // the functor is a type of struct so you have to call its constructor as the third argument. 
     std::sort(myvector.begin(), myvector.end(), MyData::compareMyDataFunctor()); 

    // Dump the vector to check the result 
     for (vector<MyData>::const_iterator citer = myvector.begin(); 
     citer != myvector.end(); ++citer) 
    {  
      cout << (*citer).m_iData << endl; 
     } 
    return 1; 
    } 

Answer 2

std::sort(v.begin(), v.end(), predicate); 

其中predicate是一个具有以下属性的函数：

用户定义的谓词函数对象，用于定义由排序中的连续元素满足的比较条件。二元谓词有两个参数，当满足时返回true，当不满意时返回false。该比较函数必须对序列中的一对元素施加严格的弱排序。

（MSDN）

例如为：

bool strings_lt_by_first_char(std::string const &x, std::string const &y) 
{ 
    return x[0] < y[0]; 
} 

Answer 3

// alg_sort.cpp 
// compile with: /EHsc 
#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); 
    } 

    int ii; 
    for (ii = 0 ; ii <= 5 ; ii++) 
    { 
     v1.push_back(2 * ii + 1); 
    } 

    cout << "Original vector v1 = (" ; 
    for (Iter1 = v1.begin() ; Iter1 != v1.end() ; Iter1++) 
     cout << *Iter1 << " "; 
    cout << ")" << endl; 

    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 
    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 
    sort(v1.begin(), v1.end(), UDgreater); 
    cout << "Resorted (UDgreater) vector v1 = (" ; 
    for (Iter1 = v1.begin() ; Iter1 != v1.end() ; Iter1++) 
     cout << *Iter1 << " "; 
    cout << ")" << endl; 
}