问题描述
你好:)
i有一个简单的（？）问题，使用我自己的密钥类型的地图。
i使用过struct重载<运营商，但是如果我用地图中不存在的密钥搜索（使用
find），我会从地图中获得现有的
键/值对。 br />
i试过这样的事情：
struct MyKey {
public：
MyKey（
unsigned short key1，
unsigned long key2）
：key1（key1），
key2（ key2）{}
bool运算符<（MyKey const& scnd）const {
return（
key1< scnd.key1 &&
key2< scnd.key2）;
};
私人：
unsigned short key1;
unsigned long key2;
};
class MyValue {
....
}
std :: map< MyKey，MyValue * MyValueList;
any想法？教程？代码示例？
谢谢&关于
asterix
首先，考虑（a）MyKey（1,10）和（b）MyKey（9,2）。哪一个比另一个少？
？然后google进行严格弱排序。提示 -
您的运营商<需要保证，但没有这样做。
祝你好运，
Tom
你能发一个问题的例子吗？以下代码似乎对我来说是好的工作：
#include< map>
using namespace std;
struct MyKey {
public：
MyKey（unsigned short key1，unsigned long key2）
： key1（key1），key2（key2）{}
bool运算符<（MyKey const& scnd）const {
return（key1< scnd.key1& ;&
key2< scnd.key2）;
};
私人：
unsigned short key1;
unsigned long key2;
};
class MyValue
{
};
int main（int argc，char * argv []）
{
map< MyKey，MyValue * MyValueList;
MyKey TestKey（0,0）; //这个键在地图中不存在
map< MyKey，MyValue *> :: iterator It = MyValueList.find（TestKey）;
if（It == MyValueList.end（））
cout<< 密钥不存在 << endl;
返回EXIT_SUCCESS;
}
你能发一个问题的例子吗？以下代码似乎对我来说是好的工作：
#include< map>
using namespace std;
struct MyKey {
public：
MyKey（unsigned short key1，unsigned long key2）
： key1（key1），key2（key2）{}
bool运算符<（MyKey const& scnd）const {
return（key1< scnd.key1& ;&
key2< scnd.key2）;
};
私人：
unsigned short key1;
unsigned long key2;
};
class MyValue
{
};
int main（int argc，char * argv []）
{
map< MyKey，MyValue * MyValueList;
MyKey TestKey（0,0）; //这个键在地图中不存在
map< MyKey，MyValue *> :: iterator It = MyValueList.find（TestKey）;
if（It == MyValueList.end（））
cout<< 密钥不存在 <<结束;
返回EXIT_SUCCESS;
}
感谢您的所有努力。
我认为问题在于，地图只能通过两个键之一来查找和排序
。例如，如果我想向地图添加第二个值
，使用相同的''key1''但不同的''key2''，则不添加的元素
到列表。
map< MyKey，MyValue * MyValueList;
MyValueList [MyKey（1,1）] = new MyValue（）;
MyValueList [MyKey（2,1）] = new MyValue（）;
MyValueList [MyKey（1,2）] = new MyValue（）;
//期望三个元素的大小但只能获得一个大小
cout<< 列表长度： << MyValueList.size（）;
hello :)
i have a simple (?) problem using maps with my own type for the key.
i have used a struct overloading the < operator, but if i search (using
find) with a key, that does not exists in the map, i get anexisting
key/value pair from the map.
i have tried something like this:
struct MyKey {
public:
MyKey(
unsigned short key1,
unsigned long key2)
:key1(key1),
key2(key2) {}
bool operator<(MyKey const& scnd) const {
return (
key1<scnd.key1 &&
key2<scnd.key2);
};
private:
unsigned short key1;
unsigned long key2;
};
class MyValue {
....
}
std::map <MyKey, MyValue*MyValueList;
any ideas? tutorials? code examples?
thanks & with regards
asterix
First, consider (a) MyKey(1, 10) and (b) MyKey(9, 2). Which one is
less than the other? Then google for "strict weak ordering." Hint -
your operator< needs to guarantee it, but fails to do so.
Best regards,
Tom
Can you post an example of your problem? The following code appears to
work fine for me:
#include <map>
using namespace std;
struct MyKey {
public:
MyKey(unsigned short key1, unsigned long key2)
:key1(key1), key2(key2) {}
bool operator<(MyKey const& scnd) const {
return (key1<scnd.key1 &&
key2<scnd.key2);
};
private:
unsigned short key1;
unsigned long key2;
};
class MyValue
{
};
int main(int argc, char *argv[])
{
map<MyKey, MyValue*MyValueList;
MyKey TestKey(0, 0); //this key does not exist in the map
map<MyKey, MyValue*>::iterator It = MyValueList.find(TestKey);
if (It == MyValueList.end())
cout << "Key does not exist" << endl;
return EXIT_SUCCESS;
}
Can you post an example of your problem? The following code appears to
work fine for me:
#include <map>
using namespace std;
struct MyKey {
public:
MyKey(unsigned short key1, unsigned long key2)
:key1(key1), key2(key2) {}
bool operator<(MyKey const& scnd) const {
return (key1<scnd.key1 &&
key2<scnd.key2);
};
private:
unsigned short key1;
unsigned long key2;
};
class MyValue
{
};
int main(int argc, char *argv[])
{
map<MyKey, MyValue*MyValueList;
MyKey TestKey(0, 0); //this key does not exist in the map
map<MyKey, MyValue*>::iterator It = MyValueList.find(TestKey);
if (It == MyValueList.end())
cout << "Key does not exist" << endl;
return EXIT_SUCCESS;
}
thanks for all your effort.
I think the problem is, that the map only looks and sorts ony by one of
the two keys. For example, if i want to add a second value to the map
with the same ''key1'' but different ''key2'', the element where not added
to the list.
map<MyKey, MyValue*MyValueList;
MyValueList[MyKey(1,1)] = new MyValue();
MyValueList[MyKey(2,1)] = new MyValue();
MyValueList[MyKey(1,2)] = new MyValue();
// expect a size of three elements but only get size of one
cout << "Length of List: " << MyValueList.size();
这篇关于以我自己的类型为关键的地图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！