Vector in C++STL c++のstlのvector

Vectors are same as dynamic arrays with the ability to resize itself automatically when an element is inserted or deleted, with their storage being handled automatically by the container. Vector elements are placed in contiguous storage so that they can be accessed and traversed using iterators. In vectors, data is inserted at the end. Inserting at the end takes differential time, as sometimes there may be a need of extending the array. Removing the last element takes only constant time because no resizing happens. Inserting and erasing at the beginning or in the middle is linear in time.vectorは動的配列であり、要素が挿入または削除されると自動的にサイズが変更され、ストレージスペースはコンテナによって自動的に制御されます.vectorの要素は順番に格納されているので、反復器を使用してアクセスしたり、遍歴したりすることができます.vectorでは、データは末尾に挿入されます.配列を拡大する必要があるため、末尾に挿入するには微分時間が必要です.最後のデータを削除するには、配列サイズが変更されていないため、定数の時間しかかかりません.開始または中間挿入または削除には線形時間がかかります.
Certain functions associated with the vectorare:vectorに関連する関数
1 Iterators

begin()-Returns an iterator pointing to the first element in the vectorはvectorの最初の要素を指す反復器(反復器の方向は最初から最後まで)を返します.この反復器の最初の要素

end(-)Returns an iterator pointing to the theoretical elementthat follows the last element in the vectorはvectorの最後の要素の反復器(反復器の方向は最初から最後まで)を返し、この反復器の最後の要素

rbegin() – Returns a reverse iterator pointing to the last element in the vector (reverse beginning). It moves from last to first elementはvectorの最後の要素の逆反復器(反復器の方向は最後から頭まで)を返します.この反復器の最初の要素は

です.

rend(-Returns a reverse iterator pointing to the theoretical element preceding the first element in the vector(considered as reverse end)はvectorの最初の要素の逆反復器(反復器方向は最後から頭まで)を返し、この反復器の最後の要素

cbegin() – Returns a constant iterator pointing to the first element in the vector.vectorの最初の要素の定数反復器を返します.(反復方向は最初から最後まで)

cend() – Returns a constant iterator pointing to the theoretical element that follows the last element in the vector.vectorの最後の要素を返す定数反復器(反復器方向は最初から最後まで)

crbegin() – Returns a constant reverse iterator pointing to the last element in the vector (reverse beginning). It moves from last to first elementはvectorの最後の要素の定数逆反復器(反復器方向は末尾から頭部)を返し、反復器は末尾から頭部

に移動する.

crend()–Returns a constant reverse iterator pointing to the theoretical element preceding the first element in the vector(considered as reverse end)vectorの最初の要素を返す定数逆反復器(反復器方向は最後から頭まで)

// C++ program to illustrate the 
// iterators in vector 
#include  
#include  

using namespace std; 

int main() 
{ 
	vector g1; 

	for (int i = 1; i <= 5; i++) 
		g1.push_back(i); 

	cout << "Output of begin and end: "; 
	for (auto i = g1.begin(); i != g1.end(); ++i) 
		cout << *i << " "; 

	cout << "
Output of cbegin and cend: "; 
	for (auto i = g1.cbegin(); i != g1.cend(); ++i) 
		cout << *i << " "; 

	cout << "
Output of rbegin and rend: "; 
	for (auto ir = g1.rbegin(); ir != g1.rend(); ++ir) 
		cout << *ir << " "; 

	cout << "
Output of crbegin and crend : "; 
	for (auto ir = g1.crbegin(); ir != g1.crend(); ++ir) 
		cout << *ir << " "; 

	return 0; 
} 

Output:

Output of begin and end: 1 2 3 4 5 
Output of cbegin and cend: 1 2 3 4 5 
Output of rbegin and rend: 5 4 3 2 1 
Output of crbegin and crend : 5 4 3 2 1

Capacity容量

size() – Returns the number of elements in the vector.戻るvectorの実際の要素数

max_size() – Returns the maximum number of elements that the vector can hold.vectorが格納できる要素の最大個数

を返します.

capacity() – Returns the size of the storage space currently allocated to the vector expressed as number of elements.要素の個数として表されるvectorに割り当てられた記憶領域のサイズを返し、vectorがサイズを指定しないことを定義し、デフォルトは8であり、サイズvector g 1を指定する(54,9).108

です

resize() – Resizes the container so that it contains ‘g’ elements.vectorのサイズを変更する

empty() – Returns whether the container is empty.容器が空の場合true

に戻る

shrink_to_fit() – Reduces the capacity of the container to fit its size and destroys all elements beyond the capacity.vectorのサイズを特定のサイズに下げ、余分な要素

を削除します.

reserve() – Requests that the vector capacity be at least enough to contain n elements.

// C++ program to illustrate the 
// capacity function in vector 
#include  
#include  

using namespace std; 

int main() 
{ 
	vector g1; 

	for (int i = 1; i <= 5; i++) 
		g1.push_back(i); 

	cout << "Size : " << g1.size(); 
	cout << "
Capacity : " << g1.capacity(); 
	cout << "
Max_Size : " << g1.max_size(); 

	// resizes the vector size to 4 
	g1.resize(4); 

	// prints the vector size after resize() 
	cout << "
Size : " << g1.size(); 

	// checks if the vector is empty or not 
	if (g1.empty() == false) 
		cout << "
Vector is not empty"; 
	else
		cout << "
Vector is empty"; 

	// Shrinks the vector 
	g1.shrink_to_fit(); 
	cout << "
Vector elements are: "; 
	for (auto it = g1.begin(); it != g1.end(); it++) 
		cout << *it << " "; 

	return 0; 
} 

Output:

Size : 5
Capacity : 8
Max_Size : 4611686018427387903
Size : 4
Vector is not empty
Vector elements are: 1 2 3 4

2 Element access:要素へのアクセス

reference operator [g] – Returns a reference to the element at position ‘g’ in the vector

at(g)-Returns a reference to the element at position‘g’in the vectorはvector中の位置gの要素

を返す.

front()-Returns a reference to the first element in the vectorはvectorの最初の要素

を返します.

back(-Returns a reference to the last element in the vectorはvectorの最後の要素

を返します.

data() – Returns a direct pointer to the memory array used internally by the vector to store its owned elements.

// C++ program to illustrate the 
// element accesser in vector 
#include  
using namespace std; 

int main() 
{ 
	vector g1; 

	for (int i = 1; i <= 10; i++) 
		g1.push_back(i * 10); 

	cout << "
Reference operator [g] : g1[2] = " << g1[2]; 

	cout << "
at : g1.at(4) = " << g1.at(4); 

	cout << "
front() : g1.front() = " << g1.front(); 

	cout << "
back() : g1.back() = " << g1.back(); 

	// pointer to the first element 
	int* pos = g1.data(); 

	cout << "
The first element is " << *pos; 
	return 0; 
} 

Output:

Reference operator [g] : g1[2] = 30
at : g1.at(4) = 50
front() : g1.front() = 10
back() : g1.back() = 100
The first element is 10

3 Modifiers:関数の変更

assign()-It assigns new value to the vector elements by replacing old ones古い値

を新しい値で上書き

push_back()–It push the elements into a vector from the back末尾から要素

を挿入

pop_back() – It is used to pop or remove elements from a vector from the back.末尾から要素

を削除

insert(-It inserts new elements before the element at the specified position特定の場所より前に要素

を挿入

erase() – It is used to remove elements from a container from the specified position or range.要素

を特定の場所から削除

swap() – It is used to swap the contents of one vector with another vector of same type and size.交換タイプとサイズが同じ2つのvector

clear()–It is used to remove all the elements of the vector container vectorのすべての要素

を削除

emplace(-It extends the container by inserting new element at position特定の場所に元素を挿入することによって容器の大きさ

を増加する

emplace_back() – It is used to insert a new element into the vector container, the new element is added to the end of the vector

// C++ program to illustrate the 
// Modifiers in vector 
#include  
#include  
using namespace std; 

int main() 
{ 
	// Assign vector 
	vector v; 

	// fill the array with 10 five times 
	v.assign(5, 10); 

	cout << "The vector elements are: "; 
	for (int i = 0; i < v.size(); i++) 
		cout << v[i] << " "; 

	// inserts 15 to the last position 
	v.push_back(15); 
	int n = v.size(); 
	cout << "
The last element is: " << v[n - 1]; 

	// removes last element 
	v.pop_back(); 

	// prints the vector 
	cout << "
The vector elements are: "; 
	for (int i = 0; i < v.size(); i++) 
		cout << v[i] << " "; 

	// inserts 5 at the beginning 
	v.insert(v.begin(), 5); 

	cout << "
The first element is: " << v[0]; 

	// removes the first element 
	v.erase(v.begin()); 

	cout << "
The first element is: " << v[0]; 

	// inserts at the beginning 
	v.emplace(v.begin(), 5); 
	cout << "
The first element is: " << v[0]; 

	// Inserts 20 at the end 
	v.emplace_back(20); 
	n = v.size(); 
	cout << "
The last element is: " << v[n - 1]; 

	// erases the vector 
	v.clear(); 
	cout << "
Vector size after erase(): " << v.size(); 

	// two vector to perform swap 
	vector v1, v2; 
	v1.push_back(1); 
	v1.push_back(2); 
	v2.push_back(3); 
	v2.push_back(4); 

	cout << "

Vector 1: "; 
	for (int i = 0; i < v1.size(); i++) 
		cout << v1[i] << " "; 

	cout << "
Vector 2: "; 
	for (int i = 0; i < v2.size(); i++) 
		cout << v2[i] << " "; 

	// Swaps v1 and v2 
	v1.swap(v2); 

	cout << "
After Swap 
Vector 1: "; 
	for (int i = 0; i < v1.size(); i++) 
		cout << v1[i] << " "; 

	cout << "
Vector 2: "; 
	for (int i = 0; i < v2.size(); i++) 
		cout << v2[i] << " "; 
} 

Output:

The vector elements are: 10 10 10 10 10 
The last element is: 15
The vector elements are: 10 10 10 10 10 
The first element is: 5
The first element is: 10
The first element is: 5
The last element is: 20
Vector size after erase(): 0

Vector 1: 1 2 
Vector 2: 3 4 
After Swap 
Vector 1: 3 4 
Vector 2: 1 2

All Vector Functions :

vector::begin() and vector::end()

vector rbegin() and rend()

vector::cbegin() and vector::cend()

vector::crend() and vector::crbegin()

vector::assign()

vector::at()

vector::back()

vector::capacity()

vector::clear()

vector::push_back()

vector::pop_back()

vector::empty()

vector::erase()

vector::size()

vector::swap()

vector::reserve()

vector::resize()

vector::shrink_to_fit()

vector::operator=

vector::operator[]

vector::front()

vector::data()

vector::emplace_back()

vector::emplace()

vector::max_size()

vector::insert()

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