deque支持的常见的操作

迈不过友情╰ 2022-06-08 13:45 150阅读 0赞

#include <iostream>
    #include <deque>
    #include <vector>
    
    using namespace std;
    
    int main(){
        //deque表示的是双端队列,删除和添加元素都在双端进行,具有队列和栈的性质,通常的队列只能在一段进行添加,另一端进行删除
        //虽然可以进行erase操作,但是性能下降会比较明显;
    
        deque<int> first;
        deque<int> second;
        deque<int> third;
        first.assign(7,100);
        deque<int>::iterator It;
        It = first.begin()+1;
        for(auto print:first){
            cout << print << " ";
        }
        cout << endl;
        second.assign(It,first.end()-1);
    
        int mytins[]={
       11,22,4,23};
        third.assign(mytins,mytins+3);
    
        cout << "Size of first: " << int(first.size()) << endl;
        cout << "Size of second: " << int(second.size()) << endl;
        cout << "Size of second: " << int(third.size()) << endl;
    
        //at操作:
        deque<int> mydeque(10);
        for(size_t i=0;i<mydeque.size();++i)
            mydeque.at(i)=i;
        for(auto print:mydeque)
            cout << print << " ";
        cout << endl;
    
        //.back():用于返回当前队列的最后一个元素
        cout << mydeque.back() << endl;
    
        //.begin() .end() 是两个迭代器
        for(auto It = mydeque.begin();It!=mydeque.end();++It)
            cout << *It << " ";
        cout << endl;
        //.cbegin() .cend() 来进行反向的迭代访问
        for(auto It=mydeque.cbegin();It!=mydeque.cend();++It)
            cout << *It << " ";
        cout << endl;
        //.clear() 用销毁当前队列里面的元素;
        mydeque.clear();
        mydeque.push_back(10);
        mydeque.push_back(1);
        mydeque.push_front(2);
        for(auto It=mydeque.begin();It!=mydeque.end();++It)
            cout << *It << " ";
        cout << endl;
        //.emplace(),通过在位置插入新元素来扩展容器,双端队列可以高效的在开头和结尾插入或者删除元素,如果在其他位置插入或
        //者删除元素,那么效率就会降低;
        deque<int> mydeque1={
       10,20,30};
        auto It1 = mydeque1.emplace(mydeque1.begin()+1,100);
        mydeque1.emplace(It1,200);
        mydeque1.emplace(mydeque1.end(),100);
        mydeque1.emplace_back(1);
        mydeque1.emplace_front(10);
    
        cout << "mydeque1 contains: ";
        for(auto print:mydeque1)
            cout << print << " ";
        cout << endl;
    
        //.empty() 用来判断是否为空的操作,返回值是一个bool值
    
        cout << boolalpha << mydeque1.empty() << noboolalpha << endl;
    
        //.erase() 支持两种操作,一种是按照位置进行删除,另一种是按照范围进行删除;
        deque<int> newdeque;
        for(size_t i=0;i<20;++i)
            newdeque.push_front(i);
        newdeque.erase(newdeque.begin()+2);
        newdeque.erase(newdeque.begin()+4,newdeque.begin()+7);
        for(auto print:newdeque)
            cout << print << " ";
        cout << endl;
    
        //.front()用于返回队列的第一个元素
        mydeque1.push_front(20);
    
        cout << mydeque1.front() << endl;
    
        //.get_allocator用于返回一个拷贝的deque关联的allocator对象
        deque<int> mydeque2;
        int *p;
        unsigned int i=0;
        p = mydeque2.get_allocator().allocate(5);
    
        for(i=0;i<5;i++)
            mydeque2.get_allocator().construct(&p[i],i);
        cout << "The allocated contains: ";
        for(i=0;i<5;i++)
            cout << p[i] << " ";
        for(i=0;i<5;i++)
            mydeque2.get_allocator().destroy(&p[i]);
        mydeque2.get_allocator().deallocate(p,5);
        //.inerst() 在某个位置精确的插入一些元素,虽然不建议这样做,但是是可以实现的;
        //下面的几种方式都是insert支持的重载函数:
        auto it = mydeque2.begin();
        mydeque2.insert(it+2,10);
        mydeque2.insert(it+2,3,1);
        vector<int> myvector(3,13);
        mydeque2.insert(mydeque2.begin()+2,myvector.begin(),myvector.end());
    
        for(auto It=mydeque2.begin();It!=mydeque2.end();++It)
            cout << *It << " ";
        cout << endl;
    
        //.max_size():当前容器所能够存放的最大值;
        cout << mydeque2.max_size() << endl;
    
        //operator=
        deque<int> newfirst(3);
        deque<int> newsecond(5);
        newsecond = newfirst;
        newfirst = deque<int>();
        cout << "Size of newfirst: " << int(newfirst.size()) << endl;
        cout << "Size of newsecond: " << int(newsecond.size()) << endl;
    
        //.[]同样说可以使用[]来访问下标元素的;
    
        //.pop_back() 用于队列的最后一个元素
        mydeque1.pop_back();
        //.pop_front()用于删除开始的第一个元素
        mydeque2.pop_front();
        //.push_back()用于在最后一个添加元素;
        mydeque2.push_back(10);
        //.push_front()用于在开始位置添加元素;
        mydeque2.push_front(20);
        //.rbegin()和rend()用来进行反向遍历;
        for(auto It=mydeque1.rbegin();It!=mydeque1.rend();++It)
            cout << *It << " ";
        cout << endl;
        //.resize() 用于更改size的大小,三种情况和vector类似;
        //.shrink_to_fit()和vector的是一样的;
        //.size()用于显示当前队列的大小;
        mydeque2.size();
        //.swap()也可以用来交换两个相同大小的双向队列;
        mydeque1.swap(mydeque2);
        return 0;
    }