8.count_if查找

#include<iostream>
using namespace std;

#include<vector>
#include<algorithm>

//count_if(iterator begin, iterator end, _Pred);按条件统计元素出现次数
//_Pred为谓词(即返回类型为bool的仿函数)

//统计内置数据类型
class Count20
{
public:
    bool operator()(const int val)
    {
        return val > 20;
    }
    
};
void test0801()
{
    vector<int> v;
    
    v.push_back(10);
    v.push_back(30);
    v.push_back(20);
    v.push_back(10);
    v.push_back(40);
    v.push_back(160);

    int cnt=count_if(v.begin(), v.end(), Count20());//使用仿函数匿名对象指定查找规则

    cout << "找到了" << cnt << "个" << endl;
}
//统计自定义数据类型
class Person
{
public:
    Person(string name,int age)
    {
        this->m_Name = name;
        this->m_Age = age;
    }
    string m_Name;
    int m_Age;
};
class CountPerson
{
public:
    bool operator()(const Person p)
    {
        if (p.m_Name == "xian")
            return true;
        return false;
    }
};
void test0802()
{
    vector<Person> v;

    Person p1("xian", 11);
    Person p2("si", 21);
    Person p3("xian", 11);
    Person p4("fan", 31);
    Person p5("xan", 41);

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

    int cnt = count_if(v.begin(), v.end(), CountPerson());//使用仿函数匿名对象指定查找规则
    cout << "找到了" << cnt << "个" <<"xian"<< endl;
}

int main()
{
    test0801();
    test0802();

    system("pause");
    return 0;
}