STL之vector

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

//打印输出
void PrintVector(vector<int>& v){
    for(vector<int>::iterator vec=v.begin(); vec!=v.end(); vec++ ){
        cout<<*vec<<" ";
    }
    cout<<endl;
}


//初始化
void test01(){
    vector<int> v1;
    int arr[] = {10,20,30,40};
    vector<int> v2(arr,sizeof(arr)/sizeof(int)+arr);
    vector<int> v3(v2.begin(),v2.end());
    vector<int> v4(v3);

    PrintVector(v2);
    PrintVector(v3);
    PrintVector(v4);

}

//常用赋值操作
void test02(){
    int arr[]={10,20,30,40};
    vector<int> v1(arr,arr+sizeof(arr)/sizeof(int));
    vector<int> v2;
    v2.assign(v1.begin(),v1.end());

    vector<int> v3;
    v3=v2;

    int arr_temp[]={100,200,300,400};
    vector<int> v4(arr_temp,arr_temp+sizeof(arr_temp)/sizeof(int));
    v4.swap(v1);
    PrintVector(v1);
    PrintVector(v2);
    PrintVector(v3);
    PrintVector(v4);
}

//大小操作
void test03(){
    int arr_temp[]={100,200,300,400};
    vector<int> v4(arr_temp,arr_temp+sizeof(arr_temp)/sizeof(int));

    cout<<"size:"<<v4.size()<<endl;//元素的个数
    if(v4.empty()){
        cout<<"空!"<<endl;
    }
    else{
        cout<<"不空!"<<endl;
    }
    PrintVector(v4);
    //v4.reserve(8);//更改capacity但不更改size
    v4.resize(6,1);//同时更改capacity和size
    PrintVector(v4);

    cout<<v4.capacity()<<endl;//元素的容量
}

//存取数据
void test04(){
    int arr_temp[]={100,200,300,400};
    vector<int> v4(arr_temp,arr_temp+sizeof(arr_temp)/sizeof(int));
    for( int i=0; i<v4.size(); i++ ){
        cout<<v4[i]<<" ";
    }
    cout<<endl;
    try{
        for( int i=0; i<v4.size()+5; i++ ){
            cout<<v4.at(i)<<" ";
        }
    }catch(...){
        cout<<"越界"<<endl;
    }
    //区别：at抛异常，[]不抛异常

    cout<<"front:"<<v4.front()<<endl;
    cout<<"back:"<<v4.back()<<endl;
}

//插入和删除
void test05(){
   vector<int> v;
   v.push_back(10);
   v.push_back(20);
   //头插法
   v.insert(v.begin(),30);
   v.insert(v.end(),40);
   PrintVector(v);
   v.insert(v.begin()+2,100);//vector支持随机访问
   //支持数组下标的，一般都支持随机访问
   PrintVector(v);
//删除操作
   v.erase(v.begin());
   PrintVector(v);
   v.erase(v.begin()+1,v.end());
   PrintVector(v);
   v.clear();
   cout<<"size:"<<v.size()<<endl;

}

//巧用swap缩减空间
void test06(){
    vector<int> v;
    for( int i=0; i<100000; i++ ){
        v.push_back(i);
    }
    cout<<"size:"<<v.size()<<endl;
    cout<<"capacity:"<<v.capacity()<<endl;

    v.resize(10);
    cout<<"-----------------"<<endl;
    cout<<"size:"<<v.size()<<endl;
    cout<<"capacity:"<<v.capacity()<<endl;

    //收缩空间
    vector<int>(v).swap(v);
    cout<<"-----------------"<<endl;
    cout<<"size:"<<v.size()<<endl;
    cout<<"capacity:"<<v.capacity()<<endl;
}

int main()
{

    test06();

    return 0;
}