B00011 unordered_map

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是一个有关unordered_map的例子程序，代码来自：std::unordered_map - cppreference.com。

unordered_map是采用哈希搜索的map。搜索速度上也许要优于map。

需要主意的是，对map对象进行遍历时，该对象有可能是未排序的。

源程序如下：

/* B00011 unordered_map */#include <iostream>#include <string>#include <unordered_map>using namespace std;int main(){    // Create an unordered_map of three strings (that map to strings)    std::unordered_map<std::string, std::string> u = {        {"RED","#FF0000"},        {"GREEN","#00FF00"},        {"BLUE","#0000FF"}    };    // Iterate and print keys and values of unordered_map    for( const auto& n : u ) {        std::cout << "Key:[" << n.first << "] Value:[" << n.second << "]\n";    }    // Add two new entries to the unordered_map    u["BLACK"] = "#000000";    u["WHITE"] = "#FFFFFF";    // Output values by key    std::cout << "The HEX of color RED is:[" << u["RED"] << "]\n";    std::cout << "The HEX of color BLACK is:[" << u["BLACK"] << "]\n";    return 0;}

程序运行结果如下：

Key:[BLUE] Value:[#0000FF]
Key:[RED] Value:[#FF0000]
Key:[GREEN] Value:[#00FF00]
The HEX of color RED is:[#FF0000]
The HEX of color BLACK is:[#000000]

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