C++primer 11.3.2节练习

练习11.20

 1 #include <iostream>
 2 #include <string>
 3 #include <set>
 4 #include <map>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <algorithm>
 8 #include <iterator>
 9
10 using namespace std;
11
12 int main()
13 {
14     map<string, int> word_count;
15     string word;
16     while (cin >> word)
17     {
18         auto ret = word_count.insert({ word, 1 });
19         if ( !ret.second )
20         {
21             ++ret.first->second;
22         }
23     }
24     for (auto c : word_count)
25     {
26         cout << c.first << " " << c.second << endl;
27     }
28     system("pause");
29     return 0;
30 }

insert的写法更加简洁。

练习11.21

拆解出来如下

1 auto ret = word_count.insert({ word,0 });
2     ++ret.first->second;

练习11.22

参数类型

1 pair<string, vector<int>>

返回类型

1 pair<map<string, vector<int>>::iterator, bool>

练习11.23

 1 #include <iostream>
 2 #include <string>
 3 #include <set>
 4 #include <map>
 5 #include <algorithm>
 6 #include <vector>
 7 #include <algorithm>
 8 #include <iterator>
 9
10 using namespace std;
11
12 int main()
13 {
14     multimap<string, vector<string>> name;
15     string first_name;
16     string lname;
17
18     while (cin >> first_name >> lname)
19     {
20         vector<string> last_name;
21         last_name.push_back(lname);
22         name.insert({ first_name, last_name });
23     }
24     for (auto c : name)
25     {
26         cout << c.first << " ";
27         for (auto w : c.second)
28             cout << w << " ";
29         cout << endl;
30     }
31     system("pause");
32     return 0;
33 }