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vector提供的元素访问及容器交换内容有如下操作：

at,访问指定的元素，同时进行越界检查

operator[]，访问指定的元素

front 访问第一个元素

back 访问最后一个元素

data 返回指向内存中数组第一个元素的指针

swap交换两个容器内容

代码示例

#include 
   
    #include 
    
     using namespace std;void getElement(){    vector
     
       vec = {1, 3, 6, 8, 9, 12};    for(int c: vec)    {        cout << c << "\t";    }    cout << endl;    cout << "vec.front = " << vec.front() << endl;    cout << "vec.at(2) = " << vec.at(2) << endl;    cout << "vec[3] ==== " << vec[3] << endl;    cout << "vec.data = " << *(vec.data()) << endl;    cout << "vec.back == " << vec.back() << endl;    cout << endl;    vector
      
        vec1;    vector
       
         vec2;    vec1.assign(3, 23);    vec2.assign({12,14,15,36,67});    for(int c: vec1)    {        cout << c << "\t";    }    cout << endl;    for(int c: vec2)    {        cout << c << "\t";    }    cout << endl;    cout << "vec1.size===" << vec1.size() << " vec1.capacity=" << vec1.capacity() << endl;    cout << "vec2.size===" << vec2.size() << " vec2.capacity=" << vec2.capacity() << endl;    auto it1 = vec1.begin();    auto it2 = vec2.begin();    int &ref1 = vec1.front();    int &ref2 = vec2.front();    cout << "*it1 = " << *it1 << " *it2 = " << *it2 << " ref1 = " << ref1 << " ref2 = " << ref2 << endl;    cout << "vec1.data = " << vec1.data() << " vec2 = " << vec2.data() << endl;    cout << "swap after======" << endl;    vec1.swap(vec2);    for(int c: vec1)    {        cout << c << "\t";    }    cout << endl;    for(int c: vec2)    {        cout << c << "\t";    }    cout << endl;    cout << "vec1.size===" << vec1.size() << " vec1.capacity=" << vec1.capacity() << endl;    cout << "vec2.size===" << vec2.size() << " vec2.capacity=" << vec2.capacity() << endl;    cout << "*it1 = " << *it1 << " *it2 = " << *it2 << " ref1 = " << ref1 << " ref2 = " << ref2 << endl;    cout << "vec1.data = " << vec1.data() << " vec2 = " << vec2.data() << endl;    cout << endl;}int main(){    //int = [-2147483648, 2147483647]    getElement();    cout << endl;    cout << "Hello World!" << endl;    return 0;}
       
      
     
    
   

运行结果：

两个容器交互后，不公元素交换了，空间大小也交换了（是交接了地址吗？swap交换原理，从结果上看，两个元素的首地址交换了，并没有重生分配空间）

注意，交换后迭代器与引用保持与原来的元素关联，例如it1指向的元素还是23，ref1引用的元素还23。

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