std::vector

成员函数

//函数签名
//default (1)
//explicit vector(const allocator_type& alloc = allocator_type());
//fill(2)
//vector(size_type n, const value_type& val,
//  const allocator_type& alloc = allocator_type());
//range(3)
//template <class InputIterator>
//vector(InputIterator first, InputIterator last,
//  const allocator_type& alloc = allocator_type());
//copy(4)
//vector(const vector& x);
//vector(const vector& x, const allocator_type& alloc);
//move(5)
//vector(vector&& x);
//vector(vector&& x, const allocator_type& alloc);
//initializer list(6)
//vector(initializer_list<value_type> il,
//  const allocator_type& alloc = allocator_type());
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector;
vector<int> second_vector(4, 100);
vector<int> third_vector(second_vector.begin(), second_vector.end());
vector<int> fourth_vector(third_vector);

int array[] = { 0,8,11 };
vector<int> my_vector(array, array + sizeof(array) / sizeof(int));

for each (auto var in my_vector)
{
cout << var << " ";
}
cout << endl;
return 0;
}

输出：

0 8 11

//函数签名
//copy(1)
//vector& operator= (const vector& x);
//move(2)
//vector& operator= (vector&& x);
//initializer list(3)
//vector& operator= (initializer_list<value_type> il);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector(8, 0);
vector<int> second_vector(11,0);

second_vector = first_vector;
first_vector = vector<int>();

cout << first_vector.size() << endl;
cout << second_vector.size() << endl;
return 0;
}

输出：

0

8

Iterators

//函数签名
//iterator begin() noexcept;
//const_iterator begin() const noexcept;
//iterator end() noexcept;
//const_iterator end() const noexcept;
//reverse_iterator rbegin();
//const_reverse_iterator rbegin() const;
//const_iterator cbegin() const noexcept;
//const_iterator cend() const noexcept;
//const_reverse_iterator crbegin() const noexcept;
//const_reverse_iterator crend() const noexcept;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector = { 0,8,11 };

for (vector<int>::iterator it = my_vector.begin(); it != my_vector.end(); it++)
cout << *it << " " ;
cout << endl;

for (vector<int>::reverse_iterator it = my_vector.rbegin(); it != my_vector.rend(); it++)
cout << *it << " ";
cout << endl;

for (vector<int>::const_iterator it = my_vector.cbegin(); it != my_vector.cend(); it++)
cout << *it << " ";
cout << endl;

for (vector<int>::const_reverse_iterator it = my_vector.crbegin(); it != my_vector.crend(); it++)
cout << *it << " ";
cout << endl;

return 0;
}

输出：

0 8 11

11 8 0

0 8 11

11 8 0

Capacity

//函数签名
//size_type size() const;
//size_type max_size() const;
//size_type capacity() const;
//void resize(size_type n, value_type val = value_type());
//bool empty() const;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector;

for (int i = 1; i <= 100; i++)
my_vector.push_back(i);

cout << my_vector.size() << endl;
//vector增长方式取决去STL的实现，绝大多数STL实现都是以成倍的方式增长，但标准并没规定
cout << my_vector.capacity() << endl;
//max_size取决于STL的实现
cout << my_vector.max_size() << endl;

//多余的直接抛弃
my_vector.resize(3);
for each (auto var in my_vector)
{
cout << var << " ";
}
cout << endl;

//不够的直接用第二个参数补齐
my_vector.resize(5, 1);
for each (auto var in my_vector)
{
cout << var << " ";
}
cout << endl;

//若不够并且没有第二个参数，则用0补齐
my_vector.resize(7);
for each (auto var in my_vector)
{
cout << var << " ";
}
cout << endl;

if (my_vector.empty())
cout << "empty vector" << endl;
else
cout << "not empty vector" << endl;

return 0;
}

输出：

100

141

1073741823

1 2 3

1 2 3 1 1

1 2 3 1 1 0 0

not empty vector

//函数签名
//void reserve (size_type n);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
//我使用的是VS2015
//vector增长方式是：1 2 3 4 6 9 13 19 28 42 63 94 141（与绝大多数以2的指数增长实现不一样）
vector<int> first_vector;
for (int i = 0; i != 100; i++)
first_vector.push_back(i);
cout << first_vector.capacity() << endl;

//如果事先知道vector要放多少个元素，则可以使用reserve()节省空间
vector<int> second_vector;
second_vector.reserve(100);
for (int i = 0; i != 100; i++)
second_vector.push_back(i);
cout << second_vector.capacity() << endl;
return 0;
}

输出：

141

100

//函数签名
//void shrink_to_fit();
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector;
for (int i = 0; i != 6; i++)
my_vector.push_back(i);
cout << my_vector.size() << endl;
cout << my_vector.capacity() << endl;

my_vector.resize(4);
cout << my_vector.size() << endl;
cout << my_vector.capacity() << endl;

//注意使用resize()并没有释放空间，必须使用
my_vector.shrink_to_fit();
cout << my_vector.size() << endl;
cout << my_vector.capacity() << endl;
return 0;
}

输出：

6

6

4

6

4

4

Element access

//函数签名
//reference operator[] (size_type n);
//const_reference operator[] (size_type n) const;
//reference at(size_type n);
//const_reference at(size_type n) const;
//reference front();
//const_reference front() const;
//reference back();
//const_reference back() const;
//value_type* data() noexcept;
//const value_type* data() const noexcept;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector(10);
for (int i = 0; i != 10; i++)
my_vector[i] = i;

for (int i = 0; i != 10; i++)
cout << my_vector.at(i) << " ";
cout << endl;

cout << my_vector.front() << endl;
cout << my_vector.back() << endl;
return 0;
}

输出：

0 1 2 3 4 5 6 7 8 9

0

9

//函数签名
//value_type* data() noexcept;
//const value_type* data() const noexcept;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector(5);
//返回一个指向数据的指针，类似一个指向数组的指针
int *p = my_vector.data();

*p = 1;
p++;
*p = 2;
//相当于p现在指向的位置+2
p[2] = 3;
for (int i = 0; i != 5; i++)
cout << my_vector[i] << " ";
cout << endl;
return 0;
}

输出：

1 2 0 3 0

Modifiers

//函数签名
//range(1)
//template <class InputIterator>
//void assign(InputIterator first, InputIterator last);
//fill(2)
//void assign(size_type n, const value_type& val);
//initializer list(3)
//void assign(initializer_list<value_type> il);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector;
vector<int> second_vector;
vector<int> third_vector;

//5个100
first_vector.assign(5, 100);
auto it = first_vector.begin() + 1;

second_vector.assign(it, first_vector.end() - 1);

int ints[] = { 0,8,11 };
third_vector.assign(ints, ints + 3);

for each (auto var in first_vector)
{
cout << var << " ";
}
cout << endl;
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;
for each (auto var in third_vector)
{
cout << var << " ";
}
cout << endl;
return 0;
}

输出：

100 100 100 100 100

100 100 100

0 8 11

//函数签名
//void push_back(const value_type& val);
//void push_back(value_type&& val);
//void pop_back();
//single element(1)
//iterator insert(const_iterator position, const value_type& val);
//fill(2)
//iterator insert(const_iterator position, size_type n, const value_type& val);
//range(3)
//template <class InputIterator>
//iterator insert(const_iterator position, InputIterator first, InputIterator last);
//move(4)
//iterator insert(const_iterator position, value_type&& val);
//initializer list(5)
//iterator insert(const_iterator position, initializer_list<value_type> il);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector;
first_vector.push_back(1);
first_vector.push_back(2);
auto it = first_vector.begin() + 1;
first_vector.insert(it, 3);

for each (auto var in first_vector)
{
cout << var << " ";
}
cout << endl;

vector<int> second_vector(3, 100);
//注意这里要重新让迭代器指向一个位置，因为插入之后会使迭代器失效
it = second_vector.begin()+2;
second_vector.insert(it,first_vector.begin()+1,first_vector.end());

for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;

int myints[] = { 6,6,6 };
second_vector.insert(second_vector.begin(),myints, myints + 3);
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;

second_vector.pop_back();
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;
return 0;
}

输出：

1 3 2

100 100 3 2 100

6 6 6 100 100 3 2 100

6 6 6 100 100 3 2

//函数签名
//iterator erase(const_iterator position);
//iterator erase(const_iterator first, const_iterator last);
//void swap(vector& x);
//template <class... Args>
//iterator emplace(const_iterator position, Args&&... args);
//template <class... Args>
//void emplace_back(Args&&... args);
//template <class... Args>
//void emplace_back(Args&&... args);
//void clear() noexcept;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector;
vector<int> second_vector;
for (int i = 1; i <= 10; i++)
first_vector.push_back(i);
//删除第四个元素
first_vector.erase(first_vector.begin() + 3);

//删除第5到第七个元素
first_vector.erase(first_vector.begin() + 4, first_vector.begin() + 6);

for each (auto var in first_vector)
{
cout << var << " ";
}
cout << endl;

first_vector.swap(second_vector);
cout << second_vector.size();
cout << endl;

//在起始位置插入一个100
second_vector.emplace(second_vector.begin(), 100);
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;

//在末尾插入一个200
second_vector.emplace_back(200);
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;

second_vector.clear();
cout << second_vector.size();
cout << endl;
return 0;
}

输出：

1 2 3 5 8 9 10

7

100 1 2 3 5 8 9 10

100 1 2 3 5 8 9 10 200

0

Allocator

//函数签名
//allocator_type get_allocator() const noexcept;
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> my_vector;
int *p;
unsigned int i;
//用vector的allocator分配五个int的空间
p = my_vector.get_allocator().allocate(5);

for (i = 0; i != 5; i++)
my_vector.get_allocator().construct(&p[i], i);

for (int i = 0; i != 5; i++)
cout << p[i] << " ";
cout << endl;

for (i = 0; i != 5; i++)
my_vector.get_allocator().destroy(&p[i]);
my_vector.get_allocator().deallocate(p,5);

return 0;
}

输出：

0 1 2 3 4

非成员函数

//函数签名
//(1)
//template <class T, class Alloc>
//bool operator== (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
//(2)
//template <class T, class Alloc>
//bool operator!= (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
//(3)
//template <class T, class Alloc>
//bool operator<  (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
//(4)
//template <class T, class Alloc>
//bool operator<= (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
//(5)
//template <class T, class Alloc>
//bool operator>  (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
//(6)
//template <class T, class Alloc>
//bool operator>= (const vector<T, Alloc>& lhs, const vector<T, Alloc>& rhs);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
vector<int> first_vector = { 1,2,3 };
vector<int> second_vector = { 3,2,1 };

if (first_vector == second_vector)
cout << "first_vector and second_vector are equal\n";
if (first_vector != second_vector)
cout << "first_vector and second_vector are not equal\n";
if (first_vector< second_vector)
cout << "first_vector is less than second_vector\n";
if (first_vector> second_vector)
cout << "first_vector is greater than second_vector\n";
if (first_vector <= second_vector)
cout << "first_vector is less than or equal to second_vector\n";
if (first_vector >= second_vector)
cout << "first_vector is greater than or equal to second_vector\n";
return 0;
}

输出：

first_vector and second_vector are not equal

first_vector is less than second_vector

first_vector is less than or equal to second_vector

//函数签名
//template <class T, class Alloc>
//void swap(vector<T, Alloc>& x, vector<T, Alloc>& y);
#include<iostream>
#include<vector>
using namespace std;
int main()
{
//非成员函数的swap()效率小于等于成员函数的swap(),所以建议用成员函数版的
vector<int> first_vector = { 1,2,3 };
vector<int> second_vector = { 3,2,1 };

swap(first_vector, second_vector);
for each (auto var in first_vector)
{
cout << var << " ";
}
cout << endl;
for each (auto var in second_vector)
{
cout << var << " ";
}
cout << endl;
return 0;
}

输出：

3 2 1

1 2 3