C++ STL 之 常用算法

Posted 2021-12-10 duxie

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

// transform 将一个容器的元素 搬运 到另一个容器中
struct MyPlus
{
    int operator()(int val)
    {
        return val + 100;
    }
};

void MyPrint(int val)
{
    cout << val << " ";
}

void test01()
{
    vector<int> v1;
    vector<int> v2;
    for (int i = 0; i < 10; i++)
    {
        v1.push_back(i);
    }
    v2.resize(v1.size()); // 开辟空间
    transform(v1.begin(), v1.end(), v2.begin(), MyPlus());
    for_each(v2.begin(), v2.end(), MyPrint);
    cout << endl;
    cout << "--------------------" << endl;
}

// 常用的查找算法
void test02()
{
    vector<int> v1;
    for (int i = 0; i < 10; i++)
    {
        v1.push_back(i);
    }
    vector<int>::iterator ret = find(v1.begin(), v1.end(), 5);
    if (ret == v1.end())
    {
        cout << "没有找到！" << endl;
    }
    else
    {
        cout << "找到了：" << *ret << endl;
    }
    cout << "--------------------" << endl;
}

class Person
{
public:
    Person(int age, int id) : age(age), id(id){}
    bool operator== (const Person& p)
    {
        return p.id == this->id && p.age == this->age;
    }
public:
    int id;
    int age;
};

void test03()
{
    vector<Person> v1;
    Person p1(10, 20), p2(20, 30);
    v1.push_back(p1);
    v1.push_back(p2);
    vector<Person>::iterator ret = find(v1.begin(), v1.end(), p1);
    if (ret == v1.end())
    {
        cout << "没有找到！" << endl;
    }
    else
    {
        cout << "找到了！" << endl;
    }
    cout << "--------------------" << endl;
}

bool MySearch(int val)
{
    return val > 5;
}

bool MySearch2(int val)
{
    return val > 5;
}

void test04()
{
    vector<int> v1;
    for (int i = 0; i < 10; i++)
    {
        v1.push_back(i);
    }
    v1.push_back(9);
    bool ret = binary_search(v1.begin(), v1.end(), 5);
    if (ret)
    {
        cout << "找到了！" << endl;
    }
    else
    {
        cout << "没有找到！" << endl;
    }

    vector<int>::iterator it = adjacent_find(v1.begin(), v1.end());
    if (it != v1.end())
    {
        cout << "找到相邻重复元素：" << *it << endl;
    }
    else
    {
        cout << "没有找到相邻重复元素!" << endl;
    }

    // find_f 会根据我们的条件(函数) ，返回第一个满足条件的元素的迭代器
    it = find_if(v1.begin(), v1.end(), MySearch);
    if (it != v1.end())
    {
        cout << "找到：" << *it << endl;
    }
    else
    {
        cout << "没有找到!" << endl;
    }

    // count count_if
    int num = count(v1.begin(), v1.end(), 9);
    cout << "9出现的次数：" << num << endl;
    num = count_if(v1.begin(), v1.end(), MySearch2);
    cout << "大于5的个数：" << num << endl;
}

int main()
{
    test01();
    test02();
    test03();
    test04();
    getchar();
    return 0;
}