C++ //count_if //按条件统计元素个数 //自定义和 内置

//按条件统计元素个数
//count_if

#include <iostream>
#include<string>
#include<vector>
#include<algorithm>

using namespace std;

class Greater20
{
public:
    bool operator()(int val)
    {
        return val > 20;
    }
};

//内置查找
void test01()
{
    vector<int>v;
    v.push_back(10);
    v.push_back(40);
    v.push_back(80);
    v.push_back(30);
    v.push_back(30); 
    v.push_back(50);
    v.push_back(20);
    v.push_back(10);


    //大于20
    int num =count_if(v.begin(), v.end(), Greater20());

    cout << "大于20的元素个数为：" << 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;
    }



    string m_Name;
    int m_Age;
};

class Greate30
{
public:
    bool operator()(const Person &p)
    {
        return p.m_Age > 30;
    }



    string m_Name;
    int m_Age;
};
void test02()
{

    vector<Person>v;
    Person p1("刘备", 30);
    Person p2("张三", 50);
    Person p3("李四", 60);
    Person p4("王五", 10);
    Person p5("曹操", 50);
    Person p6("赵云", 70);

    v.push_back(p1);
    v.push_back(p2);
    v.push_back(p3);
    v.push_back(p4);
    v.push_back(p5);
    v.push_back(p6);

    int num =count_if(v.begin(), v.end(), Greate30());
    cout << "年龄大于三十的有：" << num << endl;
}
int main()
{

    test01();
    test02();

    system("pause");
    return 0;
}