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1.前言

本篇目的：理解C++之三种key-value键值生成方式。

2.应用实例

<1>.map方式

#include <iostream>
#include <vector>
#include <map>
int main() {
  std::map<std::string, std::string> keyValueMap;

  //v1.0
  keyValueMap = { {"name", "张三"}, {"age", "20"}, {"country", "中国"} };

  // 遍历map并打印键值对
  for (const auto& pair : keyValueMap) {
    std::cout << pair.first << ": " << pair.second << std::endl;
  }
  std::cout << std::endl;

  keyValueMap.clear();

  //v2.0
  keyValueMap.insert({"name","李四"});
  keyValueMap.insert({"age","18"});
  keyValueMap.insert({"country","China"});

  //遍历map并打印键值对
  for (const auto& pair : keyValueMap) {
    std::cout << pair.first << ": " << pair.second << std::endl;
  }
  std::cout << std::endl;


  return 0;
}

<2>.vector + pair方式

#include <iostream>
#include <vector>
#include <map>
int main() {

  //vector + pair
  //v1.0
  std::vector<std::pair<std::string, std::string>> keyValuevt;
  keyValuevt = { {"name", "王五"}, {"age", "22"}, {"country", "中国"} };

  for (const auto& vv : keyValuevt) {
    std::cout << vv.first << ": " << vv.second << std::endl;
  }
  std::cout << std::endl;
  keyValuevt.clear();


  //v2.0
  keyValuevt.push_back({"name","Tom"});
  keyValuevt.push_back({"age","10"});
  keyValuevt.push_back({"countyr","China"});

  for (const auto& vv : keyValuevt) {
    std::cout << vv.first << ": " << vv.second << std::endl;
  }

  return 0;
}

<3>.vector + make_pair方式

#include <iostream>
#include <vector>
#include <map>
int main() {
  std::vector<std::pair<std::string, std::string>> keyValuevt;

  //vector + make_pair
  //v1.0
  keyValuevt.push_back(std::make_pair("name", "六五"));
  keyValuevt.push_back(std::make_pair("age", "21"));
  keyValuevt.push_back(std::make_pair("country", "中国"));

  for (const auto& vv : keyValuevt) {
    std::cout << vv.first << ": " << vv.second << std::endl;
  }
  std::cout << std::endl;
  keyValuevt.clear();
  
  //v2.0
  keyValuevt.push_back({"name","Tom"});
  keyValuevt.push_back({"age","10"});
  keyValuevt.push_back({"countyr","China"});

  for (const auto& vv : keyValuevt) {
    std::cout << vv.first << ": " << vv.second << std::endl;
  }
  return 0;
}