vector

一 用法

1.1 插入数据

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

class Man
{
public: 
    Man(int age) { this->age = age; }
private:
    int age;
}

int main()
{
    vector<int> data;
    data.push_back(1);  //尾部插入
    data.push_back(5);
    data.push_back(9);
    for (int i = 0; i < data.size(); i++)
    {
        cout << data[i] << " ";
    }
    cout << endl;

    vector<string> str;
    string s1 = "I";
    string s2 = "love";
    string s3 = "you";
    str.push_back(s1);
    str.push_back(s2);
    str.push_back(s3);
    for (int i = 0; i < str.size(); i++)
    {
        cout << str[i] << " ";
    }
    cout << endl;
	
    vector<Man> mans;
    mans.push_back(Man(18));  // 这里push_back的是新对象
	
    return 0;
}

1.2 删除数据

int main()
{
    string s1 = "张三";
    string s2 = "李四";
    string s3 = "王五";
    string s4 = "赵六";

    vector<string*> friends;
    friends.push_back(&s1);
    friends.push_back(&s2);
    friends.push_back(&s3);
    friends.push_back(&s4);

    //friends.begin() 返回一个迭代器，指向第一个成员的位置
    //friends.end() 返回一个迭代器，指向最后一个成员的下一个位置
    for (auto it = friends.begin(); it != friends.end();)
    {
        if (*it == &s3)  // 删除王五
        {
            //friends.erase() 返回一个迭代器，指向下一个成员
            it = friends.erase(it);
        }
        else
        {
            it++;
        }
    }

    for (int i = 0; i < friends.size(); i++)
    {
        cout << *(friends[i]) << endl;
    }

    return 0;
}

如果将上面删除代码修改为下面代码，会报错

    for (auto it = friends.begin(); it != friends.end();it++)
    {
        if (*it == &s3)  // 删除王五
        {
            friends.erase(it);
        }
    }

二 常见错误

注意：vector是值拷贝，如果是指针的话，是址拷贝 vector<Man*> mans;

#include <iostream>
#include <vector> 
using namespace std; 
class Man 
{ 
public: 
  Man() {} 
  void play() 
  { 
    count += 10; 
    cout << "I am playing ...." << endl; 
  }
  int getDrinkCount() const 
  { 
    return count; 
  } 
  
private: 
  int count = 0; //一共喝了多少杯酒 
};

int main(void) 
{ 
  Man zhangFei, guanYu, liuBei; 
  vector<Man> men; //这里是值拷贝，想要址拷贝，需要定义成指针类型 vector<Man*> men;
  
  // push_back 是把参数的值，拷贝给 vector 
  // men[0]的值和 liubBei 是相同的，但是，是两个不同的对象 
  men.push_back(liuBei); 
  men.push_back(guanYu); 
  men.push_back(zhangFei); 
  
  men[0].play(); 
  cout << men[0].getDrinkCount() << endl; //10 
  cout << liuBei.getDrinkCount() << endl; //0 
  
  system("pause"); 
  return 0; 
}