C++ STL map key是自定义结构体或类

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/// @file 1.cpp/// @brief /// @author EastonWoo /// 0.01/// @date 2015-11-02#include <stdio.h>#include <unistd.h>#include <semaphore.h>#include <pthread.h>#include <string>#include <map>class CKey{public:    CKey(std::string str1, std::string str2) {        this->str1 = str1;        this->str2 = str2;    }public:    std::string str1;    std::string str2;public:    bool operator<(const CKey & ct) const   // 两个const是必需的。     {        if (str1 < ct.str1) {            return true;        } else if (str1 == ct.str1) {            if ( str2 < ct.str2 ) {                return true;            }        }        return false;    }};int main(int argc, const char *argv[]){    std::map<CKey, std::string> _map;    CKey key1("11", "12");  // 被key6覆盖    CKey key6("11", "12");    CKey key5("23", "12");      CKey key7("22", "22");    CKey key2("21", "22");    CKey key3("21", "23");    CKey key4("21", "21");    _map[key1] = "hello";    _map[key2] = "world1";    _map[key3] = "world2";    _map[key4] = "world3";    _map[key5] = "world4";    _map[key6] = "world5";    _map[key7] = "world6";    for(auto it = _map.begin(); it != _map.end(); ++it) {        printf("[%s:%s]it->second = %s\n", it->first.str1.c_str(), it->first.str2.c_str(), it->second.c_str());    }        return 0;}// 编译,打印// tmp-> g++ 1.cpp -std=c++0x && ./a.out// [11:12]it->second = world5// [21:21]it->second = world3// [21:22]it->second = world1// [21:23]it->second = world2// [22:22]it->second = world6// [23:12]it->second = world4// tmp-> // //// 结果： key5 > key7 > key3 > key2 > key4 > key6 = key1//                                           key1 被 key6 覆盖
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