Unordered associative containers (C++): Difference between revisions

Revision as of 15:27, 28 June 2011

Revision as of 16:29, 29 July 2011

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It is closely related to <code>[[unordered_multimap]]</code> (available in the same header file), which is an implementation of [[multimap]] using hashing. It is also similar to <code>[[unordered_set]]</code> and <code>[[unordered_multiset]]</code>, implementations of the [[set (computer science)|set]] and [[multiset]] containers respectively and available in the <code><tr1/unordered_set></code> or <code><unordered_set></code> headers.

== UsageDescription ==

<source lang="cpp">

template<class Key,

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; [Alloc] : a function which allocates new elements.

==ExampleSample with GNU C++Code==

===Basic Usage===

<source lang="cpp">

#include <iostream>

#include <cstringstring>

#include <unordered_map>

using namespace tr1std;

#include <cstring>

namespace std {

using namespace tr1;

}

struct eqstr{

bool operator()(const char* s1, const char* s2) const {

return strcmp(s1,s2)==0;

}

};

int main()

{

std::unordered_map<const char*string, int, std::hash<const char*>, eqstr> months;

months["january"] = 31;

months["february"] = 28;

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months["november"] = 30;

months["december"] = 31;

std::cout << "september -> " << months["september"] << std::endl;

std::cout << "april -> " << months["april"] << std::endl;

std::cout << "june december -> " << months["junedecember"] << std::endl;

std::cout << "novemberfebruary -> " << months["novemberfebruary"] << std::endl;

return 0;

}