Sorted maps
What I want is a map of classes with string index to be ordered by a member of the class. According to this
https://stackoverflow.com/questions/5733254/how-can-i-create-an-own-comparator-for-a-map
I thought this would do it but I am doing something wrong.
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#include <iostream>
#include <string>
#include <map>
using namespace std;
class aaa
{
protected:
int value;
public:
aaa(void)
{
value = 0;
};
aaa(int l)
{
value = l;
};
int Value(void)
{
return value;
};
static struct ByValue: public std::binary_function<aaa, aaa, bool>
{
bool operator()(const aaa &lhs, const aaa &rhs) const
{
return lhs.value < rhs.value;
}
};
static struct ByValue2: public std::binary_function<aaa*, aaa*, bool>
{
bool operator()(const aaa *lhs, const aaa *rhs) const
{
return lhs->value < rhs->value;
}
};
};
void main(void)
{
//map<string, aaa*, aaa::ByValue2> myMap;
map<string, aaa, aaa::ByValue> myMap;
//map<string, aaa> myMap;
/*
myMap["a"] = new aaa(6);
myMap["b"] = new aaa(5);
myMap["c"] = new aaa(4);
myMap["d"] = new aaa(3);
myMap["e"] = new aaa(2);
myMap["f"] = new aaa(1);
myMap["g"] = new aaa(0);
myMap["h"] = new aaa(-1);
myMap["i"] = new aaa(-2);
myMap["j"] = new aaa(-3);
//*/
//*
myMap["a"] = aaa(6);
myMap["b"] = aaa(5);
myMap["c"] = aaa(4);
myMap["d"] = aaa(3);
myMap["e"] = aaa(2);
myMap["f"] = aaa(1);
myMap["g"] = aaa(0);
myMap["h"] = aaa(-1);
myMap["i"] = aaa(-2);
myMap["j"] = aaa(-3);
//*/
for(auto &i : myMap)
{
//cout << i.first << ":" << i.second->Value() << endl;
cout << i.first << ":" << i.second.Value() << endl;
}
system("pause");
/*delete myMap["a"];
delete myMap["b"];
delete myMap["c"];
delete myMap["d"];
delete myMap["e"];
delete myMap["f"];
delete myMap["g"];
delete myMap["h"];
delete myMap["i"];
delete myMap["j"];*/
}
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Maps are always ordered by key.
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