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 << "\ntest_multiset()......... \n";
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
[[email protected] src]# g++ -o test_multiset main.cpp pub.h test_multiset.hpp [[email protected] 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 [[email protected] 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)
原文地址：https://www.cnblogs.com/ccf19881030/p/12005134.html
时间： 2024-08-12 06:38:16