C++ stl 学习1 -- array

array是固定大小的数组，和我们用的 [ ] 形式数组差不多。

特点：

1.  只保存里面元素，连数组大小都不保存  Internally, an array does not keep any data other than the elements it contains (not even its size, which is a template parameter, fixed on compile time)

2.  大小为0是合法的，但是不要解引用。Zero-sized arrays are valid, but they should not be dereferenced (members front, back, and data).

3. 不能像其它的容器那样由分配器分配内存。(Unlike the other standard containers, arrays have a fixed size and do not manage the allocation of its elements through an allocator)

 

常见操作

array<int, 6> arr {1,2,3,4,5,6};

arr.begin()    // 第一个元素地址

Return iterator to beginning (public member function )

arr.end()     // 最后一个元素的下一个元素地址  ，和begin组合起来是数学中的[a,b) ，左闭右开区间

Return iterator to end (public member function )

arr.rbegin()     // 翻转begin

Return reverse iterator to reverse beginning (public member function )

arr.rend()       //  翻转end

Return reverse iterator to reverse end (public member function )

arr.cbegin()     // const begin的意思

Return const_iterator to beginning (public member function )

arr.cend()      // const  end的意思

Return const_iterator to end (public member function )

arr.crbegin()    //  const  rbegin 的意思

Return const_reverse_iterator to reverse beginning (public member function )

arr.crend()     //  const  rbegin 的意思

Return const_reverse_iterator to reverse end (public member function )

 

arr.size() // 大小

Return size (public member function )

arr.max_size() // 永远和arr.size()一样是初始化的那个数字即 array <int ,6> 中的6

Return maximum size (public member function )

arr.empty()  // 是否为空

Test whether array is empty (public member function )

arr[i] //不检查下标是否越界

Access element (public member function )

arr.at(i) //会检查下标是否越界

Access element (public member function )

arr.front() // 返回引用，可以当左值，第一个元素    可以arr.front() = 100 这样赋值

Access first element (public member function )

arr.back() // 返回引用，可以当左值，最后一个元素

Access last element (public member function )

arr.data() //返回指向数组首元素的指针

Get pointer to data (public member function )

Modifiers

arr.fill(num) // 把数组中所有元素都填为num

Fill array with value (public member function )

arr.swap(arr2) // 同另外一个数组交换元素，同类型，同大小

Swap content (public member function )

更详细的描述见 http://www.cplusplus.com/reference/array/array/ 

 

当反向遍历时，迭代器++ 其实是迭代器 --

 

  

#include <iostream>
#include <array>
using namespace std;

int main(void)
{
    array<int,0>  test;
    cout << test.size() << endl;     // 0
    cout << test.empty() << endl;    //是空的，返回真，1

    array<int, 6> a = {0, 1, 2, 3, 4, 5};
    for (auto i : a) {
        cout << a[i] << endl;
    }
    
    cout << a.size() << endl;        // 等于6

    for (auto it = a.data(); it != a.end(); it++) {
        cout << *it << endl;
    }
    cout << a[7] << endl;   // 不会检查是否越界，返回一个随机值
    //cout << a.at(7);    // 会检查越界，编译不过

    for (auto it = a.rbegin(); it != a.rend(); it++) {
        cout << *it << endl;     //  5  4  3  2  1  0
    }
}