【转】c++中Vector等STL容器的自定义排序

如果要自己定义STL容器的元素类最好满足STL容器对元素的要求
    必须要求:
     1、Copy构造函数
     2、赋值=操作符
     3、能够销毁对象的析构函数
    另外:
     1、可用的缺省构造函数,序列型容器必须,用于初始化元素
     2、==操作符定义,用于判断相等
     3、<操作符定义,关联型容器必须,用于缺省排序

 

你可在struct內加入 operator < ,就可以使struct有排序能力.
因為而你的pcd struct內沒有指針,所以不須要有copy constructor
和copy assignment, 編譯器會為你提供的, 你不須要自己做的.
當你要排序時只要寫 sort( obj.begin(), obj.end() )就可.

 

以上内容取自帖子:http://bbs.csdn.net/topics/40228627

另一篇参考地址:http://blog.csdn.net/tigernana/article/details/7293758

以下取自帖子:http://blog.csdn.net/guang11cheng/article/details/7556697

 

三种方式实现vector的自定义排序

方法1:重载运算符

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

using namespace std;
struct TItem
{
    int m_i32Type;
    int m_i32ID;

    bool operator <(const TItem& rhs) const // 升序排序时必须写的函数
    {
        return m_i32Type < rhs.m_i32Type;
    }
    bool operator >(const TItem& rhs) const // 降序排序时必须写的函数
    {
        return m_i32Type > rhs.m_i32Type;
    }
};
int main()
{
    vector<TItem> stItemVec;


    TItem stItem1;
    stItem1.m_i32Type = 1;
    stItem1.m_i32ID = 1;

    TItem stItem2;
    stItem2.m_i32Type = 2;
    stItem2.m_i32ID = 2;

    TItem stItem3;
    stItem3.m_i32Type = 3;
    stItem3.m_i32ID = 3;

    TItem stItem4;
    stItem4.m_i32Type = 2;
    stItem4.m_i32ID = 4;

    stItemVec.push_back(stItem1);
    stItemVec.push_back(stItem2);
    stItemVec.push_back(stItem3);
    stItemVec.push_back(stItem4);

    // 升序排序
    sort(stItemVec.begin(), stItemVec.end(), less<TItem>()); 
    // 或者sort(ctn.begin(), ctn.end());   默认情况为升序

    for (size_t i = 0; i < stItemVec.size(); i++)
        printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);

    printf("--\n");

    // 降序排序
    sort(stItemVec.begin(), stItemVec.end(), greater<TItem>());

    for (size_t i = 0; i < stItemVec.size(); i++)
        printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);

    return 0;
}

方法2:全局的比较函数

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

using namespace std;
 

struct TItem
 {
     int m_i32Type;
     int m_i32ID;
 };
 

bool lessmark(const TItem& stItem1, const TItem& stItem2)
 {
     return stItem1.m_i32Type < stItem2.m_i32Type;
 }
 

bool greatermark(const TItem& stItem1, const TItem& stItem2)
 {
     return stItem1.m_i32Type > stItem2.m_i32Type;
 }
 

int main()
 {
     vector<TItem> stItemVec;
 

    TItem stItem1;
     stItem1.m_i32Type = 1;
     stItem1.m_i32ID = 1;
 

    TItem stItem2;
     stItem2.m_i32Type = 2;
     stItem2.m_i32ID = 2;
 

    TItem stItem3;
     stItem3.m_i32Type = 3;
     stItem3.m_i32ID = 3;
 

    TItem stItem4;
     stItem4.m_i32Type = 2;
     stItem4.m_i32ID = 4;
 

    stItemVec.push_back(stItem1);
     stItemVec.push_back(stItem2);
     stItemVec.push_back(stItem3);
     stItemVec.push_back(stItem4);
 

    sort(stItemVec.begin(), stItemVec.end(), lessmark); //升序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);
 

    printf("--\n");
 

    sort(stItemVec.begin(), stItemVec.end(), greatermark); //降序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);
 

    return 0;
 }
 

方法3:函数对象

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

using namespace std;
 

struct TItem
 {
     int m_i32Type;
     int m_i32ID;
 };
 

class CompLess
 {
 public:
     bool operator ()(const TItem& stItem1, const TItem& stItem2)
     {
         return stItem1.m_i32Type < stItem2.m_i32Type;
     }
 };
 

class CompGreater
 {
 public:
     bool operator ()(const TItem& stItem1, const TItem& stItem2)
     {
         return stItem1.m_i32Type > stItem2.m_i32Type;
     }
 };
 

int main()
 {
     vector<TItem> stItemVec;
 

    TItem stItem1;
     stItem1.m_i32Type = 1;
     stItem1.m_i32ID = 1;
 

    TItem stItem2;
     stItem2.m_i32Type = 2;
     stItem2.m_i32ID = 2;
 

    TItem stItem3;
     stItem3.m_i32Type = 3;
     stItem3.m_i32ID = 3;
 

    TItem stItem4;
     stItem4.m_i32Type = 2;
     stItem4.m_i32ID = 4;
 

    stItemVec.push_back(stItem1);
     stItemVec.push_back(stItem2);
     stItemVec.push_back(stItem3);
     stItemVec.push_back(stItem4);
 

    sort(stItemVec.begin(), stItemVec.end(), CompLess()); //升序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);
 

    printf("--\n");
 

    sort(stItemVec.begin(), stItemVec.end(), CompGreater()); //降序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i].m_i32Type, stItemVec[i].m_i32ID);
 

    return 0;
 }
 

/*
 结果如下:
 type: 1, id: 1
 type: 2, id: 2
 type: 2, id: 4
 type: 3, id: 3
 --
 type: 3, id: 3
 type: 2, id: 2
 type: 2, id: 4
 type: 1, id: 1
 可以看出vector的sort的稳定的。
 */

问题:

1,示例代码中只有>和<关系处理,==关系是如何推导出来的?

2,排序时要移动元素,效率怎样?

3,如果自定义结构定义在一个类的内部,使用函数对象进行排序,这个函数对象可以作为类的成员函数吗?

4,在上面的例子中,vector中存放的都是结构(对象)本身,如果存放的是结构指针,该如何排序呢?此时只能通过全局的比较函数或者函数对象来做,且比较函数的参数要是指针类型的,如下:

(1)全局的比较函数

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

using namespace std;
 

struct TItem
 {
     int m_i32Type;
     int m_i32ID;
 };
 

bool CompLess(const TItem* pstItem1, const TItem* pstItem2)
 {
     return pstItem1->m_i32Type < pstItem2->m_i32Type;
 }
 

bool CompGreater(const TItem* pstItem1, const TItem* pstItem2)
 {
     return pstItem1->m_i32Type > pstItem2->m_i32Type;
 }
 

int main()
 {
     vector<TItem*> stItemVec;
 

    TItem stItem1;
     stItem1.m_i32Type = 1;
     stItem1.m_i32ID = 1;
 

    TItem stItem2;
     stItem2.m_i32Type = 2;
     stItem2.m_i32ID = 2;
 

    TItem stItem3;
     stItem3.m_i32Type = 3;
     stItem3.m_i32ID = 3;
 

    TItem stItem4;
     stItem4.m_i32Type = 2;
     stItem4.m_i32ID = 4;
 

    stItemVec.push_back(&stItem1);
     stItemVec.push_back(&stItem2);
     stItemVec.push_back(&stItem3);
     stItemVec.push_back(&stItem4);
 

    sort(stItemVec.begin(), stItemVec.end(), CompLess); //升序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i]->m_i32Type, stItemVec[i]->m_i32ID);
 

    printf("--\n");
 

    sort(stItemVec.begin(), stItemVec.end(), CompGreater); //降序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i]->m_i32Type, stItemVec[i]->m_i32ID);
 
    return 0;
 }

  (2)函数对象

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

using namespace std;
 

struct TItem
 {
     int m_i32Type;
     int m_i32ID;
 };
 

class CompLess
 {
 public:
     bool operator ()(const TItem* pstItem1, const TItem* pstItem2)
     {
         return pstItem1->m_i32Type < pstItem2->m_i32Type;
     }
 };
 

class CompGreater
 {
 public:
     bool operator ()(const TItem* pstItem1, const TItem* pstItem2)
     {
         return pstItem1->m_i32Type > pstItem2->m_i32Type;
     }
 };
 

int main()
 {
     vector<TItem*> stItemVec;
 

    TItem stItem1;
     stItem1.m_i32Type = 1;
     stItem1.m_i32ID = 1;
 

    TItem stItem2;
     stItem2.m_i32Type = 2;
     stItem2.m_i32ID = 2;
 

    TItem stItem3;
     stItem3.m_i32Type = 3;
     stItem3.m_i32ID = 3;
 

    TItem stItem4;
     stItem4.m_i32Type = 2;
     stItem4.m_i32ID = 4;
 

    stItemVec.push_back(&stItem1);
     stItemVec.push_back(&stItem2);
     stItemVec.push_back(&stItem3);
     stItemVec.push_back(&stItem4);
 

    sort(stItemVec.begin(), stItemVec.end(), CompLess()); //升序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i]->m_i32Type, stItemVec[i]->m_i32ID);
 

    printf("--\n");
 

    sort(stItemVec.begin(), stItemVec.end(), CompGreater()); //降序排序
 

    for (size_t i = 0; i < stItemVec.size(); i++)
         printf("type: %d, id: %d\n", stItemVec[i]->m_i32Type, stItemVec[i]->m_i32ID);
 

    return 0;
 }

  

posted @ 2014-08-26 16:13  编程小翁  阅读(2614)  评论(0编辑  收藏  举报
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