c++ - 我如何遍历 map vector

Question

我编码是为了乐趣。我创建了一个 map vector ，看看我可以用容器做什么。当我遍历 vector 时，只有 Alfred 和 Angela 出现。如何显示所有 名称？有可能吗？这是我目前所拥有的:

#include <map>
#include <iostream>
#include <conio.h>
#include <vector>
#include <string>

int main()
{
    //create a map
    std::map<std::string, unsigned int> mySuperCoolMap;
    mySuperCoolMap["Edward"] = 39;
    mySuperCoolMap["Daniel"] = 35;
    mySuperCoolMap["Carlos"] = 67;
    mySuperCoolMap["Bobby"]  =  8;
    mySuperCoolMap["Alfred"] = 23;

    std::cout << "\n\n";

    //Ranged based for loop to display the names and age
    for (auto itr : mySuperCoolMap)
    {
        std::cout << itr.first << " is: " << itr.second << " years old.\n";
    }

    //create another map
    std::map<std::string, unsigned int> myOtherSuperCoolMap;
    myOtherSuperCoolMap["Espana"]  =  395;
    myOtherSuperCoolMap["Dominic"] = 1000;
    myOtherSuperCoolMap["Chalas"]  =  167;
    myOtherSuperCoolMap["Brian"]   =  238;
    myOtherSuperCoolMap["Angela"]  = 2300;

    //Display the names and age
    for (auto itr : myOtherSuperCoolMap)
    {
        std::cout << itr.first << " is: " << itr.second << " years old.\n";
    }

    //create a vector of maps
    std::vector<std::map<std::string, unsigned int>> myVectorOfMaps;

    myVectorOfMaps.push_back(mySuperCoolMap);
    myVectorOfMaps.push_back(myOtherSuperCoolMap);

    std::cout << "\n\n";

    //Display the values in the vector
    for (auto itr : myVectorOfMaps)
    {
        std::cout << itr.begin()->first << " is: " << itr.begin()->second << " years old.\n";
    }

    _getch();
    return 0;
}

Answer 1

您需要使用嵌套循环。使用调试器并打印 itr如果您正在学习新概念，可能会给您这种直觉。

//Display the values in the vector
for (const auto &vec : myVectorOfMaps)
{
    for (const auto &p : vec)
    {
        std::cout << p.first << " is: " << p.second << " years old.\n";
    }
}

Demo

你要求只打印第一个元素，这就是为什么你只得到第一个元素。请注意，这是一个错误，因为您在访问 map 的第一个元素时未确保 map 是否为非空。

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^{注意 <conio.h>不是标准 header ，可能不适用于标准平台}