STL标准库-容器-deque

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deque双向开口可进可出的容器

我们知道连续内存的容器不能随意扩充,因为这样容易扩充别人那去

deque却可以,它创造了内存连续的假象.

其实deque由一段一段构成 ,他是分段连续,而不是内存连续 当走向段的尾端时候自动跳到下一段 所以支持迭代器++ 操作,自动跳到下一段的方法由operator++实现

deque每次扩充 申请一个段

一 定义

头文件 #include <deque>

int main_0() {

    //默认构造函数 创建一个空的deque
    deque<int> c;

    //拷贝构造
    deque<int> c1(c);

    //赋值拷贝
    deque<int> c2 = c1;

    //指定元素个数创建
    deque<int> c3 (5,6);
    for (auto i : c3) {
        cout<< i << ",";
    }
    cout << "deque(个数, 元素)"<<endl;

    //指定区间创建
    deque<int> c4(c3.begin()+2, c3.begin()+3);
    for (auto i : c4) {
        cout<< i << ",";
    }
    cout << "deque(区间, 区间)"<<endl;

    //指定初始化列表创建
    deque<int> c5({2,3,4,5});
    for (auto i : c5) {
        cout<< i << ",";
    }
    cout << "deque({})"<<endl;

    //指定初始化列表创建
    deque<int> c6 = {2,3,4,5};
    for (auto i : c6) {
        cout<< i << ",";
    }
    cout << "deque = {}" <<endl;
    cout<<endl;
    return 0;
}

int main()
{
    deque<int> c = {1,2,3,4,5};
    deque<int> c1;

    // 赋值初始化
    c1.assign(c.begin(),c.end());
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "assign()" <<endl;

    //在尾部插入
    c1.push_back(6);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "push_back()" <<endl;

    //头插入
    c1.push_front(0);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "push_front()" <<endl;

    //弹尾元素
    c1.pop_back();
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "pop_back()" <<endl;

    //弹头元素
    c1.pop_front();
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "pop_front()" <<endl;

    //指定位置插入元素
    c1.insert(c1.begin()+3, 10);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "insert()" <<endl;

    //删除指定位置元素
    c1.erase(c1.begin()+3);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "erase()" <<endl;

    //清空deque
    c.clear();
    for (auto i: c) {
        cout<< i << ",";
    }
    cout << "clear()" <<endl;

    //构造
    c1.emplace(c1.end(), 100);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "emplace()" <<endl;

    //头位置插入元素
    c1.emplace_front(111);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "emplace_front()" <<endl;

    //尾位置插入元素
    c1.emplace_back(111);
    for (auto i: c1) {
        cout<< i << ",";
    }
    cout << "emplace_back()" <<endl;

    //交换
    c.swap(c1);
    for (auto i: c) {
        cout<< i << ",";
    }
    cout << "swap()" <<endl;

    int tmp;
    tmp = c.front();
    cout<<"第一个元素"<< tmp << endl;

    tmp = c.back();
    cout<<"最后一个元素"<< tmp << endl;

    tmp = c.at(1);
    cout<<"指定下标元素"<< tmp << endl;

    tmp = c[1];
    cout<<"指定[]下标元素"<< tmp << endl;

    return 0;
}

int main()
{
    deque<int> c = {1,2,3,4,5};

    //元素个数
    cout<< "size(): " << c.size() <<endl;

    //重新设定deque大小 少退多补
    c.resize(10, 5);
    for(auto i : c)
    {
        cout << i <<",";
    }
    cout << "resize()" << endl;

    //最大容量
    cout << "max_size(): " << c.max_size() <<endl;

    //是否为空
    cout << "empty: " << c.empty() << endl;

    //清空内存
    c.shrink_to_fit();

    return 0;
}

int main()
{
    deque<int> c = {1,2,3,4,5};
    //指向第一个元素的迭代器
    cout << *c.begin() << endl;
    //指向最后一个元素的下一个位置的迭代器
    cout << *c.end() << endl;
    //反向deque的第一个元素的迭代器
    cout << *c.rbegin() << endl;
    //反向deque的第一个元素的上一个位置迭代器
    cout << *c.rend() << endl;
    //指向第一个元素的迭代器
    cout << *c.cbegin() << endl;
    //指向最后一个元素的下一个位置的迭代器
    cout << *c.cend() << endl;
    //反向deque的第一个元素的迭代器
    cout << *c.crbegin() << endl;
    //反向deque的第一个元素的上一个位置迭代器
    cout << *c.crend() << endl;

    return 0;
}