【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; }