18.2.4【STL常用查找算法count】 

 1 #include<iostream>
 2 #include<cstdlib>
 3 using namespace std;
 4 #include<vector>
 5 #include<algorithm>
 6 #include<string>
 7 
 8 
 9 /*
10      5.2.5 count
11         统计元素个数
12         count(iterator beg, iterator end, value);
13         // 统计元素出现次数
14         // beg 开始迭代器
15         // end 结束迭代器
16         // value 统计的元素
17         统计自定义数据类型时候，需要配合重载 operator==
18 */
19 
20 
21 void test525() //内置数据类型
22 {
23     vector<int> v;
24     v.push_back(1);
25     v.push_back(2);
26     v.push_back(4);
27     v.push_back(5);
28     v.push_back(2);
29     v.push_back(4);
30     v.push_back(4);
31     v.push_back(3);
32     v.push_back(4);
33 
34     int num = count(v.begin(), v.end(), 4);
35     cout << "num of 4 in v:" << num << endl;
36 }
37 
38 
39 class Person
40 {
41 public:
42     string name;
43     int age;
44 
45 public:
46     Person(string _name, int _age)
47     {
48         this->name = _name;
49         this->age = _age;
50     }
51 
52     bool operator==(const Person & p)
53     {
54         if(this->age == p.age)
55         {
56             return true;
57         }
58         return false;
59     }
60 };
61 
62 
63 void test525_1() //自定义数据类型
64 {
65     vector<Person> vv;
66     Person p1("aaa", 10);
67     Person p2("bbb", 20);
68     Person p3("ccc", 30);
69     Person p4("ddd", 30);
70     Person p5("eee", 40);
71     Person p6("fff", 30);
72     vv.push_back(p1);
73     vv.push_back(p2);
74     vv.push_back(p3);
75     vv.push_back(p4);
76     vv.push_back(p5);
77     vv.push_back(p6);
78 
79     Person p("zzz", 30); //统计vv中跟zzz年龄相同的有多少人
80     int num = count(vv.begin(), vv.end(), p);
81     cout << "num:" << num << endl;
82 }
83 
84 
85 int main()
86 {
87     test525();
88     test525_1();
89 
90     system("pause");
91     return 0;
92 }

 

posted @ 2021-05-13 11:50  yub4by  阅读(83)  评论(0)    收藏  举报