C++count

功能描述：

统计元素个数

函数原型：

count(iterator beg, iterator end, value);

//统计元素出现次数

//beg开始迭代器

//end开始迭代器

//value统计的元素

代码示例：

#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
//常用查找算法count
void test01()
{
   
       vector<int>v;
       v.push_back(10);
       v.push_back(40);
       v.push_back(30);
       v.push_back(40);
       v.push_back(20);
       v.push_back(40);
       int num = count(v.begin(), v.end(), 40);
       cout << "40的元素个数为：" << num << endl;
}
class Person
{
   
public:
       Person(string name, int age)
       {
   
              this->m_Name = name;
              this->m_Age = age;
       }
       bool operator==(const Person &p)
       {
   
              if (this->m_Age == p.m_Age)
              {
   
                     return true;
              }
              else
              {
   
                     return false;
              }
       }
       string m_Name;
       int m_Age;
};
void test02()
{
   
       vector<Person>v;
       Person p1("刘备", 35);
       Person p2("关羽",35);
       Person p3("张飞", 35);
       Person p4("赵云", 30);
       Person p5("曹操", 40);
       //将人员插入到容器中
       v.push_back(p1);
       v.push_back(p2);
       v.push_back(p3);
       v.push_back(p4);
       v.push_back(p5);
       Person p("诸葛亮", 35);
       int num = count(v.begin(), v.end(), p);
       cout << "和诸葛亮岁数一样的人员个数为" << num << endl;
}
int main()
{
   
       //test01();
       test02();
       system("pause");
       return 0;
}

总结：统计自定义数据类型，需要配合重载operator==