map和multimap都自帶find(),不需Generic Algorithm就可搜尋,事實上,當container和algorithm都提供方法時,應先考慮使用container自帶的方法,因為algorithm考慮到泛型,還需要經過iterator,但container自帶的方法卻是量身訂做的,所以執行速度較快。
要列出multimap中某個key的所有value,有三種方式,此範例demo如何使用這三種方式。
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/*
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(C) OOMusou 2006 http://oomusou.cnblogs.com
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Filename : MultiMapFindByKey.cpp
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Compiler : Visual C++ 8.0 / ISO C++
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Description : Demo how to find by key in multimap
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Release : 12/16/2006 1.0
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*/
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#include <iostream>
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#include <map>
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#include <string>
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using namespace std;
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int main() {
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typedef multimap<string, string> AuthorBooks;
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AuthorBooks authorBooks;
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authorBooks.insert(make_pair("Stanley B. Lippman", "C++ Primer"));
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authorBooks.insert(make_pair("Stanley B. Lippman", "Essentail C++"));
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authorBooks.insert(make_pair("Scott Meyers", "Effective C++"));
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authorBooks.insert(make_pair("Andrei Alexandrescu", "Modern C++ Design"));
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string searchItem = "Stanley B. Lippman";
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// Find all values by key using count & find
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AuthorBooks::size_type entries = authorBooks.count(searchItem);
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AuthorBooks::iterator iter = authorBooks.find(searchItem);
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for(AuthorBooks::size_type cnt = 0; cnt != entries; ++cnt)
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cout << iter++->second << endl;
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cout << endl;
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cout << endl;
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// Find all values by key using lower_bound(), upper_bound();
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AuthorBooks::iterator beg = authorBooks.lower_bound(searchItem);
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AuthorBooks::iterator end = authorBooks.upper_bound(searchItem);
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while(beg != end)
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cout << beg++->second << endl;
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cout << endl;
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cout << endl;
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// Find all values by key using equal_range()
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typedef AuthorBooks::iterator iterAB;
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pair<iterAB, iterAB> pos = authorBooks.equal_range(searchItem);
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while(pos.first != pos.second)
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cout << pos.first++->second << endl;
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return 0;
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}
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除了使用count() + find()程式碼較多外,lower_bound()/upper_bound()和equal_range()程式碼都差不多長,所以沒有特別建議。