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 结束迭代器
// value 统计的元素
#include <iostream> #include <algorithm> #include <vector> using namespace std; void test01() { vector<int> v; v.push_back(1); v.push_back(2); v.push_back(4); v.push_back(5); v.push_back(3); v.push_back(4); v.push_back(4); int num = count(v.begin(), v.end(), 4); cout << "4的个数为： " << num << endl; } //自定义数据类型 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; } } public: 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", 37); Person p4("赵云", 20); Person p5("曹操", 35); 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 << "num = " << num << endl; } int main() { //test01(); test02(); return 0; } //统计自定义数据类型的时候，需要配合重载operator==