1.需求, 現在10個執行緒分別列印AAA... BBB... CCC...要求按順序列印, 如圖所示

Plan1:

 1 #define THREAD_CNT 5
 2 
 3 std::condition_variable g_cvs[THREAD_CNT];
 4 std::condition_variable g_cv;
 5 std::mutex g_mtx;
 6 
 7 int g_curIndex = -1;
 8 
 9 void PrintChar(char ch)
10 {
11     int index = ch - 'A';
12     int sleepMsTime = rand() % 2000
 
;
13     printf("%c ready\n", ch);
14     std::this_thread::sleep_for(std::chrono::milliseconds(sleepMsTime));
15     printf("%c lock\n", ch);
16     std::unique_lock<std::mutex> lg(g_mtx);
17     while (1)
18     {
19         g_cv.wait(lg);
20         if (g_curIndex == index)
21         {
22             break
 
;
23         }
24     }
25     printf("%c unlock\n", ch);
26     printf("\n");
27     for (int i = 0; i < 10; ++i)
28     {
29         printf("%c", ch);
30     }
31     printf("\n");
32     ++g_curIndex;
33     g_cv.notify_all();
34 }
35 
36 
37 int main()
38 {
39     srand(time(nullptr));
40     std::vector<std::thread> vecThreads;
 
41     for (int i = 0; i < THREAD_CNT; ++i)
42     {
43         vecThreads.push_back(std::thread(PrintChar, i + 'A'));
44     }
45     std::this_thread::sleep_for(std::chrono::milliseconds(3000));
46     g_curIndex = 0;
47     g_cv.notify_all();
48     for (auto &t : vecThreads)
49     {
50         t.join();
51     }
52     return 0;
53 }

Plan2:

 1 #define THREAD_CNT 5
 2 
 3 std::condition_variable g_cvs[THREAD_CNT];
 4 std::condition_variable g_cv;
 5 std::mutex g_mtx;
 6 
 7 void PrintChar(char ch)
 8 {
 9     int index = ch - 'A';
10     int sleepMsTime = rand() % 2000;
11     printf("%c ready\n", ch);
12     std::this_thread::sleep_for(std::chrono::milliseconds(sleepMsTime));
13     printf("%c lock\n", ch);
14     std::unique_lock<std::mutex> lg(g_mtx);
15 
16     g_cvs[index].wait(lg);
17 
18     printf("%c unlock\n", ch);
19     printf("\n");
20     for (int i = 0; i < 10; ++i)
21     {
22         printf("%c", ch);
23     }
24     printf("\n");
25     if (index != THREAD_CNT - 1)
26     {
27         g_cvs[index + 1].notify_one();
28     }
29 }
30 
31 
32 int main()
33 {
34     srand(time(nullptr));
35     std::vector<std::thread> vecThreads;
36     for (int i = 0; i < THREAD_CNT; ++i)
37     {
38         vecThreads.push_back(std::thread(PrintChar, i + 'A'));
39     }
40     std::this_thread::sleep_for(std::chrono::milliseconds(3000));
41     g_cvs[0].notify_one();
42     for (auto &t : vecThreads)
43     {
44         t.join();
45     }
46     return 0;
47 }