vector的使用-蒲公英云

#include<iostream>
#include <vector>
using namespace std;
int main(){
    unsigned int i;
    vector<int> first;
    vector<int> second(4,100);
    vector<int> third(second.begin(),second.end());
    vector<int> forth{
   0,1,2,3,4,5,6,7,8,9,0};
    int mytins[]={
   16,2,22,7,11};
    vector<int> fifth(mytins,mytins+sizeof(mytins)/sizeof(int));
    cout << "the fifth contains ";
    for(auto h:fifth)
        cout << h << " ";
    cout << endl;
    //assign()函数一共包含两个版本第一个支持重复数字的引用版本,第二个支持迭代器版本;
    first.assign(7,100);
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    first.assign(10,1);
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    first.assign(second.begin(),second.end());
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    first.assign(second.begin(),second.end());
    //at用来作为下标访问
    for(size_t i=0;i<forth.size();++i)
        cout << forth.at(i) << " ";
    cout << endl;
    //.back()用于返回当前vector的最后一个元素;
    cout << forth.back() << endl;
    //.begin() .end()两个迭代器,用于访问vector里面的元素
    for(auto It=forth.begin();It!=forth.end();++It)
        cout << *It << " ";
    cout << endl;
    //auto 可以使用vector<int>::iterator It 进行代替;
    //capacity() vector里面已经分配的空间的大小,用来衡量里面可以访问多少元素;
    cout << "first.capacity(): " << first.capacity() <<"\tfirst.size(): " << (int)first.size() << endl;  
    cout << "second.capacity(): " << second.capacity() <<"\tsecond.size(): " << second.size() << endl; 
    cout << "third.capacity(): " << third.capacity() <<"\tthird.size(): " << third.size() << endl;  
    cout << "forth.capacity(): " << forth.capacity() <<"\tforth.size(): " << forth.size() << endl;  
    cout << "fifth.capacity(): " << fifth.capacity() <<"\tfifth.size(): " << fifth.size() << endl;  
    //clear 调用析构函数,将所有元素清0,并且将size置为0,但是分配的空间大小是没有改变的;
    first.clear();
    cout << first.capacity() << endl;
    cout << first.size() << endl;
    //.erase()擦出某些函数,一共有两个版本,其中一个是传递位置,另一个是传递范围,两者都必须是迭代器
    for(size_t i=0;i<20;++i)
        first.push_back(i);
    first.erase(first.begin()+2);
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    first.erase(first.begin()+2,first.begin()+7);
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    //.front()用于返回当前容器的第一个元素;
    cout << "first.front(): " << first.front() << endl;
    //.get_allocator()用于获得分配容器的适配器,可以使用这个适配器用来获得需要的空间;
    int *p;
    vector<int> myvector;
    //使用指针获得5个元素的分配地址;
    p=myvector.get_allocator().allocate(5);
    for(auto i=0;i<5;++i)
        p[i]=i;
    for(auto i=0;i<5;++i)
        cout << p[i] << " ";
    cout << endl;
    //Insert 用于在当前容器里面插入元素,支持三种形式的插入:(位置,元素),(位置,元素数量,元素),(位置,迭代器开始,迭代器结束);
    forth.insert(forth.begin()+5,10);
    forth.insert(forth.begin()+3,4,5);
    forth.insert(forth.begin()+7,first.begin(),first.end());
    for(auto h:forth)
        cout << h << " ";
    cout << endl;
    //=用于完成元素的拷贝,并且丢弃原来数组里面的元素
    vector<int> vfirst;
    first=vfirst;
    for(auto h:first)
        cout << h << " ";
    cout << endl;
    for(size_t i=0;i<forth.size();++i)
        forth[i]=i*2;
    for(size_t i=0;i<forth.size();++i)
        cout << forth[i] << " ";
    cout << endl;
    //.pop.back()用于逐个的删除容器里面的元素;
    while(second.empty()){
        second.pop_back();
    }
    //.rebegin() rend()用于从后往前进行迭代器的遍历;
    for(auto It=forth.rbegin();It!=forth.rend();++It)
        cout << *It << " ";
    cout << endl;
    //用来主动要求capacity的大小,函数原型void reverse(size_t n);
    vector<int> newvector;
    newvector.resize(20);
    cout << "newvector.capacity: " << newvector.capacity() << endl;
    //.resize():一共有三种情况,如果设定的n的值小于当前的数字元素实际大小,那么超过的部分就会被销毁;
    //如果n大于当前实际元素的大小,那么容器里面会被填充其他的元素;
    //如果n大于capacity的大小,那么容器会自动调整capacity的大小;
    vector<int> mynewvector;
    for(size_t i=0;i<10;i++)
        mynewvector.push_back(i);
    mynewvector.resize(5);
    mynewvector.resize(8,100);
    for(auto my:mynewvector)
        cout << my << " ";
    cout << endl;
    //.shrink_to_fit:请求减少capacity适应size的大小;
    //这个过程使可以自动进行优化的,有可能进行空间的重新分配,但是不会原始的数据;
    vector<int> mynewvector1(100);
    cout << "capacity of mynewvector1: " << mynewvector1.capacity() << endl;
    mynewvector1.resize(10);
    cout << "capacity of mynewvector1: " << mynewvector1.capacity() << endl;
    myvector.shrink_to_fit();
    cout << "capacity of mynewvector1: " << mynewvector1.capacity() << endl;
    //size:用来衡量容器里面实际元素的数量
    cout << "myvector.size(): " << myvector.size() << endl;
    //.swap()用来交换两个容器里面的元素
    second.swap(fifth);
    cout << "second contains: " ;
    for(auto nh:second)
        cout << nh << " ";
    cout << endl;
    cout << "fifth contains: ";
    for(auto hh:fifth)
        cout << hh << " ";
    cout << endl;
}