C++ stl 学习6-- deque

deque 双端队列，不同于vector是一块连续的区间，deque是一组独立区块, 不是所有元素像vector那样都连续，中间有部分不是相邻的。所以不建议用指针访问，建议用迭代器。

 

resize()  //  改变deque的大小，n小于当前size 则保留前n个，n大于当前size则将其它的元素设置为0或者指定值

If n is smaller than the current container size, the content is reduced to its first n elements, removing those beyond (and destroying them).

If n is greater than the current container size, the content is expanded by inserting at the end as many elements as needed to reach a size of n. If val is specified, the new elements are initialized as copies of val, otherwise, they are value-initialized.

#include <iostream>
#include <deque>
using namespace std;
int main()
{

    deque<int> a;
    a.assign({1,3,5,7,8});
    a.push_back(12);   // 1  3 5 7 8 12
    a.resize(3);   //  1  3  5 后面的元素还在但是不属于容器了
    a.emplace(begin(a), 6);  // 6 1 3 5
    cout << a[4] << endl;    // 7

    auto it = a.insert(end(a), 66);  // 6 1 3 5  66  it 指向66
    it = a.erase(it);    //  it 指向end

    for (auto i : a) {
        cout << i << endl;
    }
    return 0;
}