vector insertion and deletion
Function description:
Insert and delete operations on vector containers
Function prototype:
push_back(ele); //尾部插入元素ele
pop_back(); //删除最后一个元素
insert(const_iterator pos, ele); //迭代器指向位置pos插入元素ele
insert(const_iterator pos, int count ,ele); //迭代器指向位置pos插入count个元素ele
erase(const_iterator pos); //删除迭代器指向的元素
erase(const_iterator start, const_iterator end); //删除迭代器从start到end之间的元素
clear(); //删除容器中所有元素
#include<iostream>
using namespace std;
#include<vector>
//vector插入和删除
/*
push_back(ele); //尾部插入元素ele
pop_back(); //删除最后一个元素
insert(const_iterator pos, ele); //迭代器指向位置pos插入元素ele
insert(const_iterator pos, int count ,ele); //迭代器指向位置pos插入count个元素ele
erase(const_iterator pos); //删除迭代器指向的元素
erase(const_iterator start, const_iterator end); //删除迭代器从start到end之间的元素
clear(); //删除容器中所有元素
*/
void printVector(vector<int>& v)
{
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
cout << endl;
}
void test01()
{
vector<int>v1;
//尾插
v1.push_back(10);
v1.push_back(40);
v1.push_back(30);
v1.push_back(50);
v1.push_back(20);
//遍历
printVector(v1);
//尾删
v1.pop_back();
printVector(v1);
//插入 第一个参数是迭代器
v1.insert(v1.begin(), 100);
printVector(v1);
v1.insert(v1.begin(), 2, 333);
printVector(v1);
//删除
v1.erase(v1.begin());
printVector(v1);
//清空
//v1.erase(v1.begin(),v1.end());
v1.clear();
printVector(v1);
}
int main()
{
test01();
return 0;
}
Summary:
tail insert push_back
tail delete pop_back
insert insert (position iterator)
delete erase (position iterator)
clear clear
vector data access
Function description:
access to the data in the vector
Function prototype:
at(int idx); //返回索引idx所指的数据
operator[]; //返回索引idx所指的数据
front(); //返回容器中第一个数据元素
back(); //返回容器中最后一个数据元素
#include<iostream>
using namespace std;
#include<vector>
//vector容器 数据存取
void printVector(vector<int>& v)
{
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
cout << endl;
}
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; ++i)
{
v1.push_back(i);
}
//利用[]方式访问数组中元素
for (int i = 0; i < v1.size(); ++i)
{
cout << v1[i] << " ";
}
cout << endl;
//利用at方式访问元素
for (int i = 0; i < v1.size(); ++i)
{
cout << v1.at(i) << " ";
}
cout << endl;
//获取第一个元素
cout << "第一个元素为：" << v1.front() << endl;
//获取最后一个元素
cout << "最后一个元素为：" << v1.back() << endl;
}
int main()
{
test01();
return 0;
}
Summary:
In addition to using iterators to obtain elements in the vector container, [] and at can also
return the first element of the container to the front
and return the last element of the container
vector swap container
Function description:
realize the exchange of elements in two containers
Function prototype:
swap(vec); //Swap vec with its own elements
#include<iostream>
using namespace std;
#include<vector>
//vector容器互换
void printVector(vector<int>& v)
{
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
cout << endl;
}
//1、基本使用
void test01()
{
vector<int>v1;
for (int i = 0; i < 10; ++i)
{
v1.push_back(i);
}
cout << "交换前：" << endl;
printVector(v1);
vector<int>v2;
for (int i = 10; i > 0; --i)
{
v2.push_back(i);
}
printVector(v2);
cout << "交换后：" << endl;
v1.swap(v2);
printVector(v1);
printVector(v2);
}
//2、实际用途
//巧用swap可以收缩内存空间
void test02()
{
vector<int>v;
for (int i = 0; i < 100000; i++)
{
v.push_back(i);
}
cout << "v的容量为：" << v.capacity() << endl;
cout << "v的大小为：" << v.size() << endl;
v.resize(3); //重新指定大小
cout << "v的容量为：" << v.capacity() << endl;
cout << "v的大小为：" << v.size() << endl;
//巧用swap收缩内存
vector<int>(v).swap(v);
cout << "v的容量为：" << v.capacity() << endl;
cout << "v的大小为：" << v.size() << endl;
}
int main()
{
test01();
test02();
return 0;
}
Summary: swap can make two containers interchangeable, which can achieve a practical effect of shrinking memory
Vector reserved space
Function description:
reduce the expansion times of vector when dynamically expanding capacity
Function prototype:
reserve(int len); // The container reserves len element length, the reserved position is not initialized, and the element is inaccessible
#include<iostream>
using namespace std;
#include<vector>
//vector容器 预留空间
void printVector(vector<int>& v)
{
for (vector<int>::iterator it = v.begin(); it != v.end(); it++)
{
cout << *it << " ";
}
cout << endl;
}
void test01()
{
vector<int>v;
//int num = 0;//统计开辟次数
//int* p = NULL;
//for (int i = 0; i < 100000; ++i)
//{
// v.push_back(i);
// if (p != &v[0])
// {
// p = &v[0];
// num++;
// }
//}
//cout << "num = " << num << endl;//30
//利用reserve预留空间
v.reserve(100000);
int num = 0;//统计开辟次数
int* p = NULL;
for (int i = 0; i < 100000; ++i)
{
v.push_back(i);
if (p != &v[0])
{
p = &v[0];
num++;
}
}
cout << "num = " << num << endl;//1
}
int main()
{
test01();
return 0;
}
Summary: If the amount of data is large, you can use reserve to reserve space at the beginning