最近在Bilibili上看到不少侯捷老师C++的视频教程，侯捷老师翻译了很多C++的经典书籍，比如《Essential C++中文版》、《STL源码剖析》，也写了《深入浅出MFC 第二版》。
使用到multiset这个关联容器时，本来以为Visual Studio2017中会提供#include <multiset>这个头文件，没想到加入到显示错误，后来查了下资料，说是multiset只是set的一个特例而已，只需要包含set的头文件即可，使用#include<set>即可。使用multimap时是也是类似的，需要包含#inlcude<map>头文件。
## 测试代码如下：
// test_multiset.hpp
1 #ifndef _TEST_MULTISET_H 2 #define _TEST_MULTISET_H 3 4 #include <set> 5 #include <stdexcept> 6 #include <string> 7 #include <iostream> 8 #include <ctime> 9 #include <cstdio> // snprintf() 10 #include <cstdlib> // abort() 11 #include <algorithm> 12 13 #include "pub.h" 14 15 using std::multiset; 16 using std::cin; 17 using std::cout; 18 using std::endl; 19 using std::string; 20 using std::exception; 21 using std::find; 22 using std::sort; 23 24 namespace jj06 25 { 26 void test_multiset(long& totalCount) 27 { 28 cout << " test_multiset()......... "; 29 30 multiset<string> c; 31 char buf[10]; 32 clock_t timeStart = clock(); 33 for (long i = 0; i < totalCount; ++i) 34 { 35 try { 36 snprintf(buf, 10, "%d", rand() % 65535); 37 c.insert(string(buf)); 38 } 39 catch (std::exception& e) { 40 41 cout << "i=" << i << e.what() << endl; 42 abort(); 43 } 44 } 45 46 cout << "milli-seconds:" << (clock() - timeStart) << endl; 47 cout << "multiset.size()= " << c.size() << endl; 48 cout << "multiset.max_size()= " << c.max_size() << endl; 49 50 string target = get_a_target_string(); 51 { 52 timeStart = clock(); 53 auto pItem = ::find(c.begin(), c.end(), target); // 比c.find(...)慢很多 54 cout << "::find(), mill-seconds: " << (clock() - timeStart) << endl; 55 56 if (pItem != c.end()) 57 cout << "found, " << *pItem << endl; 58 else 59 cout << "not found! " << endl; 60 } 61 62 { 63 timeStart = clock(); 64 auto pItem = c.find(target); // 比::find(...)快很多 65 cout << "c.find(), mill-seconds: " << (clock() - timeStart) << endl; 66 67 if (pItem != c.end()) 68 cout << "found, " << *pItem << endl; 69 else 70 cout << "not found! " << endl; 71 } 72 } 73 } 74 #endif
// pub.h
1 #ifndef _PUB_H_ 2 #define _PUB_H_ 3 4 #ifdef _MSC_VER 5 #define snprintf _snprintf 6 #endif 7 8 #include <string> 9 #include <cstdio> 10 #include <iostream> 11 12 using std::string; 13 using std::cin; 14 using std::cout; 15 16 //const long ASIZE = 1000000; 17 const long ASIZE = 50000; 18 19 long get_a_target_long() 20 { 21 long target = 0; 22 cout << "target (0~" << RAND_MAX << "): "; 23 cin >> target; 24 25 return target; 26 } 27 28 string get_a_target_string() 29 { 30 long target = 0; 31 char buf[10]; 32 33 cout << "target (0~" << RAND_MAX << "): "; 34 cin >> target; 35 snprintf(buf, 10, "%d", target); 36 37 return string(buf); 38 } 39 int compareLongs(const void* a, const void* b) 40 { 41 return (*(long*)a - *(long*)b); 42 } 43 44 int compareStrings(const void* a, const void* b) 45 { 46 if (*(string*)a > *(string*)b) 47 return 1; 48 else if(*(string*)a < *(string*)b) 49 return -1; 50 else 51 return 0; 52 } 53 #endif
// main.cpp
1 #include "test_multiset.hpp" 2 int main(int argc, char* argv[]) 3 { 4 long totalCount; 5 cout << "how many elements:"; 6 cin >> totalCount; 7 8 srand((unsigned)time(NULL)); 9 jj06::test_multiset(totalCount); 10 11 getchar(); 12 13 return 0; 14 }
## 运行示例
[root@192 src]# g++ -o test_multiset main.cpp pub.h test_multiset.hpp [root@192 src]# ./test_multiset how many elements:1000000 test_multiset()......... milli-seconds:9750000 multiset.size()= 1000000 multiset.max_size()= 461168601842738790 target (0~2147483647): 23456 ::find(), mill-seconds: 50000 found, 23456 c.find(), mill-seconds: 0 found, 23456 [root@192 src]# 、
## 完整的代码见本人的Github：
[stl_container_test](https://github.com/ccf19881030/stl_container_test)
### 附带侯捷老师B站的C++相关视频链接地址：
* [C++ STL与泛型编程高级-侯捷](https://www.bilibili.com/video/av48068999?p=6)
* [C++面向对象高级编程（侯捷）](https://www.bilibili.com/video/av27135524)
* [C++标准11-14](https://www.bilibili.com/video/av51795083)