15. STL-常用算法

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5.1 常用遍历算法

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for_each

for_each(iterator beg, iterator end,_func)

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void print01(int val)
{
    cout << val << " ";
}

class print02
{
public:
    void operator()(int val)
    {
        cout << val << " ";
    }
};
void test01()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }

    for_each(v.begin(), v.end(), print01);
    cout << endl;
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

transform

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搬运要提前开辟空间，否则无法搬运

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class TransForm
{
public:
    int operator()(int v)
    {
        return v;
    }
};
void test02()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    vector<int> t;
    t.resize(v.size());
    transform(v.begin(), v.end(), t.begin(),TransForm());
    for_each(t.begin(), t.end(), print02());
}
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5.2 常用查找算法

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5.2.1 find

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void test03()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    vector<int>::iterator it = find(v.begin(), v.end(), 5);
    if (it == v.end())
    {
        cout << "don't" << endl;
    }
    else
    {
        cout << *it << endl;
    }

    for_each(v.begin(), v.end(), print02());
}

class Person
{
public:
    Person(string mn, int ma) :name(mn), age(ma) {}

    bool operator==(const Person&p)
    {
        if (this->name == p.name && this->age ==p.age)
        {
            return true;
        }
        return false;
    }
    string name;
    int age;
};
void test04()
{
    vector<Person> v;
    Person p1("a", 10);
    Person p2("b", 20);
    Person p3("c", 30);
    Person p4("d", 40);

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


    Person pp("b", 20);
    vector<Person>::iterator it = find(v.begin(), v.end(), pp);
    if (it == v.end())
    {
        cout << "no" << endl;

    }
    else
    {
        cout << it->age << " " << it->name << endl;
    }

}

5.2.2 find_if

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class GreaterFive
{
public:

    bool operator()(int val)
    {
        return val > 5;
    }
};
void test06()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    vector<int>::iterator it = find_if(v.begin(), v.end(), GreaterFive());
    if (it == v.end())
    {
        cout << "don't" << endl;
    }
    else
    {
        cout << *it << endl;
    }

    for_each(v.begin(), v.end(), print02());
}

5.2.3 adjacant_find

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void test07()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    v.push_back(9);
    vector<int>::iterator it = adjacent_find(v.begin(), v.end());
    if (it == v.end())
    {
        cout << "don't" << endl;
    }
    else
    {
        cout << *it << endl;
    }

    for_each(v.begin(), v.end(), print02());
}
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void test08()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    cout << binary_search(v.begin(), v.end(),9) << endl;

    for_each(v.begin(), v.end(), print02());
}

5.2.5 count

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要重载 ==

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class Person2
{
public:
    Person2(string mn, int ma) :name(mn), age(ma) {}

    bool operator==(const Person2& p)
    {
        if (this->age == p.age)
        {
            return true;
        }
        return false;
    }
    string name;
    int age;
};
void test10()
{
    vector<Person2> v;
    Person2 p("zhang", 10);
    for (int i = 0; i < 10; i++)
    {
        v.push_back(p);
    }
    Person2 p2("zhang", 10);
    cout << count(v.begin(), v.end(), p2) << endl;

5.2.6 count_if

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void test11()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(20);
    }
    cout << count_if(v.begin(), v.end(), GreaterFive()) << endl;

    for_each(v.begin(), v.end(), print02());
}
class Person3
{
public:
    Person3(string mn, int ma) :name(mn), age(ma) {}

    
    string name;
    int age;
};

class Less20
{
public:
    bool operator()(const Person3& p)
    {
        if (p.age < 20)
            return true;
        return false;
    }
};
void test12()
{
    vector<Person3> v;
    Person3 p("zhang", 10);
    for (int i = 0; i < 10; i++)
    {
        v.push_back(p);
    }
    cout << count_if(v.begin(), v.end(), Less20()) << endl;

}

5.3 常用排序算法

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5.3.1 sort

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void test13()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    v.push_back(-2);
    for_each(v.begin(), v.end(), print02());
    cout << endl;

    sort(v.begin(), v.end());
    for_each(v.begin(), v.end(), print02());
    cout << endl;

    sort(v.begin(), v.end(), greater<int>());
    for_each(v.begin(), v.end(), print02());
    cout << endl;

}

5.3.2 random_shuffle

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void test14()
{
    srand((unsigned int)time(NULL));
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    v.push_back(-2);
    for_each(v.begin(), v.end(), print02());
    cout << endl;

    random_shuffle(v.begin(), v.end());
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

5.3.3 merge

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void test15()
{
    vector<int> v;
    vector<int> t;
    vector<int> vt;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    for (int i = 0; i < 10; i++)
    {
        t.push_back(i+1);
    }
    // 提前分配空间
    vt.resize(v.size() + t.size());
    merge(v.begin(), v.end(), t.begin(), t.end(), vt.begin());
    for_each(vt.begin(), vt.end(), print02());
    cout << endl;
}

5.3.4 reverse

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void test16()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    
    // 提前分配空间
    reverse(v.begin(), v.end());
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

5.4 常用拷贝和替换算法

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5.4.1 copy

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void test17()
{
    vector<int> v;
    vector<int> t;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }

    // 提前分配空间
    t.resize(v.size());
    copy(v.begin(), v.end(),t.begin());
    for_each(t.begin(), t.end(), print02());
    cout << endl;
}

5.4.2 replace

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void test18()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }

    replace(v.begin(), v.end(), 9,10);
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

5.4.3 replace_if

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void test18()
{
    vector<int> v;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }

    // 提前分配空间

    replace_if(v.begin(), v.end(), GreaterFive(), 10);
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

5.4.4 swap

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void test20()
{
    vector<int> v;
    vector<int> t;
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    for (int i = 0; i < 10; i++)
    {
        t.push_back(i*2);
    }
    // 提前分配空间
    swap(v, t);
    for_each(v.begin(), v.end(), print02());
    cout << endl;
    for_each(t.begin(), t.end(), print02());
    cout << endl;
}

5.5 常用算术生成算法

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5.5.1accumulate

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void test21()
{
    vector<int> v;
    
    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    int total  = accumulate(v.begin(),v.end(),0);
    for_each(v.begin(), v.end(), print02());
    cout << endl;
    cout << total << endl;
}

5.5.2 fill

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void test22()
{
    vector<int> v;

    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    fill(v.begin(), v.end(), 20);
    for_each(v.begin(), v.end(), print02());
    cout << endl;
}

5.6常用集合算法

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5.6.1 set intersection

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返回值为交集最后一个元素的指针

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void test23()
{
    vector<int> v;
    vector<int> t;
    vector<int> vt;

    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    for (int i = 0; i < 10; i++)
    {
        t.push_back(i + 5);
    }
    vt.resize(min(v.size(), t.size()));
    vector<int>::iterator it =  set_intersection(v.begin(), v.end(), t.begin(), t.end(), vt.begin());
    for_each(vt.begin(), it, print02());
    cout << endl;
}

5.6.2 set_union

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void test24()
{
    vector<int> v;
    vector<int> t;
    vector<int> vt;

    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    for (int i = 0; i < 10; i++)
    {
        t.push_back(i + 5);
    }
    vt.resize((v.size()+t.size()));
    vector<int>::iterator it = set_union(v.begin(), v.end(), t.begin(), t.end(), vt.begin());
    for_each(vt.begin(), it, print02());
    cout << endl;
}

5.6.3 set_diffrence

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void test25()
{
    vector<int> v;
    vector<int> t;
    vector<int> vt;

    for (int i = 0; i < 10; i++)
    {
        v.push_back(i);
    }
    for (int i = 0; i < 10; i++)
    {
        t.push_back(i + 5);
    }
    vt.resize(max(v.size() , t.size()));
    vector<int>::iterator it = set_difference(v.begin(), v.end(), t.begin(), t.end(), vt.begin());
    for_each(vt.begin(), it, print02());
    cout << endl;
}
c++ > c++ 黑马
#c++
15. STL-常用算法
http://binbo-zappy.github.io/2024/11/27/cpp/15-STL-常用算法/
作者
Binbo
发布于
2024年11月27日
许可协议