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c++ vector的遍历

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发布于 2021-07-05 07:41:54

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文章被收录于专栏：Python编程 pyqt matplotlibPython编程 pyqt matplotlib

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代码可运行

vector 是C++标准模板库中的一个类模板。

用vector<typename> v 可以声明一个元素类型为typename的容器类模板v。
v.push_back(）函数可以向容器v的尾部添加一个元素。
vector<typename>::iterator it 声明一个迭代器it。it是一个指向typename型数据的指针，可用于遍历vector。
v.begin() 指向vector第一个元素。
v.end(）指向vector 最后一个元素的后一个位置。

练习的源码如下:

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


class Book
{
    friend ostream& operator<<(ostream& o, Book& b);
public:
    string name;
    float price;
    string author;
    Book(string name, float price, string author)
    {
        this->name = name;
        this->price = price;
        this->author = author;
    }
};
ostream& operator<<(ostream& o, Book& b)
{
    o<< b.name;
    return o;
}


void func(Book& b)
{
    cout<<b.name<<endl;
}


void test1()
{
    vector<float> v;
    v.push_back(1);
    v.push_back(2);
    v.push_back(3);
    v.push_back(4);


    for(vector<float>::iterator it = v.begin(); it!=v.end(); it++)
    {
        cout<< *it << endl;
    }
}


void test1_1()
{
    vector<Book> v;
    Book b1("天", 50, "哈哈");
    Book b2("人", 40, "嘻嘻");
    Book b3("地", 40, "嘿嘿");
    v.push_back(b1);
    v.push_back(b2);
    v.push_back(b3);


    //用algorithm 库的for_each 迭代，对每一元素循环调用func
    for_each(v.begin(), v.end(), func);
}
void test2()
{


    Book b1("天", 50, "哈哈");
    Book b2("人", 40, "嘻嘻");
    Book b3("地", 40, "嘿嘿");
    vector<Book> v;
    v.push_back(b1);
    v.push_back(b2);
    v.push_back(b3);


    for(vector<Book>::iterator it = v.begin(); it!=v.end(); it++)
    {
        cout<< *it << endl;
    }
}


void test3()
{
    //vector 的元素为指向对象的指针。
    Book b1("天", 50, "哈哈");
    Book b2("人", 40, "嘻嘻");
    Book b3("地", 40, "嘿嘿");
    vector<Book*> v;
    v.push_back(&b1);
    v.push_back(&b2);
    v.push_back(&b3);


    for(vector<Book*>::iterator it = v.begin(); it!=v.end(); it++)
    {
        cout<< **it << endl;
        cout<< (*it)->author << endl; //-> 优先级比 * 高
    }
}


void test4()
{
    Book b1("天", 50, "哈哈");
    Book b2("地", 40, "嘻嘻");
    Book b3("人", 40, "嘿嘿");
    vector<Book*> v1;
    v1.push_back(&b1);
    v1.push_back(&b2);
    v1.push_back(&b3);


    vector<Book*> v2;
    v2.push_back(&b3);
    v2.push_back(&b2);
    v2.push_back(&b1);


    //嵌套vector的用法
    vector <vector<Book*>> V;
    V.push_back(v1);
    V.push_back(v2);


    for(vector <vector<Book*>>::iterator it_outter = V.begin(); it_outter!= V.end(); it_outter++)
    {
        vector<Book*> v = *it_outter;
        for(vector<Book*>::iterator it_inner = v.begin(); it_inner!= v.end(); it_inner++)
        {
            cout<< (*it_inner)->author<<" ";//-> 优先级比 * 高
        }
        cout<<endl;
    }


}


int main()
{
    test1_1();
    //test3();
    test4();


    return 0;
}