assign vector c

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Std::vector<t,allocator>:: assign.

Replaces the contents of the container.

All iterators, pointers and references to the elements of the container are invalidated. The past-the-end iterator is also invalidated.

[ edit ] Parameters

[ edit ] complexity, [ edit ] example.

The following code uses assign to add several characters to a std:: vector < char > :

[ edit ] See also

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C++ vector assign() 使用方法及示例

C++ Vector(容器)

此函数为向量（vector）分配新值，并替换旧值。

要为其分配值的向量（vector）v。语法为：

（first，last）：它定义了范围。将区间（first,last）的元素赋值到当前的vector容器中。

val ：它定义要分配的值。

让我们看一个简单的实例。

在该示例中，使用assign()函数将包含整数值的向量（vector）v分配给向量（vector）v1。

让我们看另一个简单的实例。

在此示例中，使用assign()函数为v分配了五次“ C”值。

在该示例中，使用assign()函数将包含字符值的向量（vector）v分配给向量（vector）v1。

std::vector assign() method

since C++20
since C++11
until C++11

Replaces the contents of the container with the contents of another.

(1) Replaces the contents with count copies of value value .

(2) Replaces the contents with copies of those in the range [ first, last ) .

The behavior is undefined

This overload participates in overload resolution only if InputIt satisfies LegacyInputIterator .

This overload has the same effect as overload (1) if InputIt is an integral type.

(3) Replaces the contents with the elements from the initializer list ilist .

All iterators , pointers and references to the elements of the container are invalidated. The past-the-end iterator is also invalidated.

Parameters

count - the new size of the container
value - the value to initialize elements of the container with
first , last - the range to copy the elements from
ilist - initializer list to copy the values from

Return value

Complexity .

(1) Linear in count - O(count) .
(2) Linear in distance between first and last - O(std::distance(firs,t last)) .
(3) Linear in ilist.size() - O(ilist.size()) .

Exceptions

Return value

std::vector:: assign

Replaces the contents of the container.

1) replaces the contents with count copies of value value

2) replaces the contents with copies of those in the range [first, last)

3) replaces the contents with the elements from the initializer list ilist .

[ edit ] Parameters

[ edit ] complexity.

1) linear in count

2) linear in distance between first and last

3) linear in ilist. size ( )

[ edit ] Example

The following code uses assign to add several characters to a std:: vector < char > :

[ edit ] See also

The C Standard Library
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C++ Vector Library - assign() Function

Description.

The C++ function std::vector::assign() assign new values to the vector elements by replacing old ones. It modifies size of vector if necessary.

If memory allocation happens allocation is allocated by internal allocator.

Declaration

Following is the declaration for std::vector::assign() function form std::vector header.

n − Size of vector.

val − Value for each element.

Return value

This member function never throws exception.

Time complexity

Linear i.e. O(n)

The following example shows the usage of std::vector::assign() function.

Let us compile and run the above program, this will produce the following result −

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<cassert> (assert.h)
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C++11 <cfenv> (fenv.h)
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<ciso646> (iso646.h)
<climits> (limits.h)
<clocale> (locale.h)
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<csetjmp> (setjmp.h)
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member functions

vector::assign
vector::back
vector::begin
vector::capacity
C++11 vector::cbegin
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vector::pop_back
vector::push_back
vector::rbegin
vector::rend
vector::reserve
vector::resize
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non-member overloads

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swap (vector)

std:: vector ::operator=

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Home » C++ STL

vector::assign() function with example in C++ STL

C++ STL vector::assign() function : Here, we are going to learn about the assign() function of vector header in C++ STL with example . Submitted by IncludeHelp , on May 15, 2019

C++ vector::assign() function

vector::assign() is a library function of "vector" header, it is used to initialize a vector or assign content to a vector, it assigns the new content to the vector, update the existing content, and also resizes the vector's size according to the content.

Note: To use vector, include <vector> header.

Syntax of vector::assign() function

Parameter(s):

In case of type 1: iterator_first, iterator_last – are the first and last iterators of a sequence with them we are going to assign the vector. In case of type 2: n – is the size of the vector and value – is a constant value to be assigned.

Return value: void – In both of the cases it returns nothing.

C++ program to demonstrate example of vector::assign() function

Reference: C++ vector::assign()

<vector>

Std:: vector ::assign, return value, iterator validity, exception safety.

Information
<cassert> (assert.h)
<cctype> (ctype.h)
<cerrno> (errno.h)
<cfenv> (fenv.h)
<cfloat> (float.h)
<cinttypes> (inttypes.h)
<ciso646> (iso646.h)
<climits> (limits.h)
<clocale> (locale.h)
<cmath> (math.h)
<csetjmp> (setjmp.h)
<csignal> (signal.h)
<cstdarg> (stdarg.h)
<cstdbool> (stdbool.h)
<cstddef> (stddef.h)
<cstdint> (stdint.h)
<cstdio> (stdio.h)
<cstdlib> (stdlib.h)
<cstring> (string.h)
<ctgmath> (tgmath.h)
<ctime> (time.h)
<cuchar> (uchar.h)
<cwchar> (wchar.h)
<cwctype> (wctype.h)

Containers:

<array>
<deque>
<forward_list>
<list>
<map>
<queue>
<set>
<stack>
<unordered_map>
<unordered_set>

Input/Output:

<fstream>
<iomanip>
<ios>
<iosfwd>
<iostream>
<istream>
<ostream>
<sstream>
<streambuf>

Multi-threading:

<atomic>
<condition_variable>
<future>
<mutex>
<thread>
<algorithm>
<bitset>
<chrono>
<codecvt>
<complex>
<exception>
<functional>
<initializer_list>
<iterator>
<limits>
<locale>
<memory>
<new>
<numeric>
<random>
<ratio>
<regex>
<stdexcept>
<string>
<system_error>
<tuple>
<typeindex>
<typeinfo>
<type_traits>
<utility>
<valarray>
vector<bool>
vector::vector
vector::~vector

member functions:

vector::assign
vector::back
vector::begin
vector::capacity
vector::cbegin
vector::cend
vector::clear
vector::crbegin
vector::crend
vector::data
vector::emplace
vector::emplace_back
vector::empty
vector::end
vector::erase
vector::front
vector::get_allocator
vector::insert
vector::max_size
vector::operator=
vector::operator[]
vector::pop_back
vector::push_back
vector::rbegin
vector::rend
vector::reserve
vector::resize
vector::shrink_to_fit
vector::size
vector::swap

non-member overloads:

relational operators (vector)
swap (vector)

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vectorのresizeとassignの違い

c++の vector では resize と assign という機能があります。僕は今まで resize ではサイズの指定だけ、 assign はサイズと中身、とイメージしていたんですが resize でも要素を指定できることを知ったので忘れないために違いを書いておこうと思います。

※簡単のため std:: を省略しています。

このようにするとaの中身は {1,2,3,0,0} になります。 resize で増えた分は0になります。

このようにするとaの中身は {1} になります。 resize で指定した長さになるまで erase が行われるらしいです。

これが僕がこの記事を書こうと思った原因です。 resize って名前だから長さしか指定できないだろうと思ったらそんなことありませんでした。このようにするとaの中身は {1,2,3,10,10} になります。埋める際に指定した要素になります。縮んだ場合は要素を指定しても変わりません。

このようにするとaの中身は {1,1,1,1,1} になります。 assign では全ての要素を指定した要素で埋めます。

このようにするとaの中身は {1} になります。伸びた場合と同様です。

リストで assign やほかの vector のイテレータなども assign は受け取ります。

resize や assign でメモリが解放されるわけではないことに注意が必要です。

とした場合、配列の中身は {1,2,3,4,5} と5要素しかありませんがメモリ領域は6要素分確保されています。元が4,追加で2なので6です。新しく追加した場合はもともとのメモリ領域分の半分が新たに確保されます。

先ほどの状態からこのようにするとメモリ領域が5要素分になります。使っていないメモリを開放することができます。また、

このように swap のメンバ関数で使っていないメモリの解放をすることができます。新しく vector 配列を作って中身を移動させています。

参考にさせていただいたサイトの方々です。より詳しく書かれています。2つ目の記事は vector そのものを開放したい場合に参考にしてください。

https://programming.pc-note.net/cpp/vector.html https://qiita.com/sawasaka/items/2df474fc00ec2105acab

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How to Add Element to Vector of Pairs in C++?

In C++, vectors are dynamic arrays that can grow and shrink in size whereas a pair is a container that can store two data elements or objects. A vector of pairs, therefore, is a dynamic array of pairs. In this article, we will learn how to add an element to a vector of pairs in C++.

Adding to a Vector of Pairs in C++

We can add an element to a vector of pairs using the vector::std::push_back() function that will append the pair passed inside the function at the end of the vector i.e. after its current last element.

Syntax to Add Element to Vector of Pairs in C++

C++ program to add element to vector of pairs.

The below program demonstrates how we can add an element in a vector of pairs in C++.

Time Complexity: O(1) Auxiliary Space: O(n), where n is the total number of pairs added to the vector.

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std::vector<T,Allocator>::assign
std::vector<T,Allocator>:: assign. Replaces the contents of the container. 1) Replaces the contents with count copies of value value. 2) Replaces the contents with copies of those in the range [first,last). The behavior is undefined if either argument is an iterator into *this . This overload has the same effect as overload (1) if InputIt is an ...
vector
Assign vector content Assigns new contents to the vector , replacing its current contents, and modifying its size accordingly. In the range version (1), the new contents are elements constructed from each of the elements in the range between first and last , in the same order.
vector :: assign() in C++ STL
vector:: assign () is an STL in C++ which assigns new values to the vector elements by replacing old ones. It can also modify the size of the vector if necessary. The syntax for assigning constant values: vectorname.assign(int size, int value) Parameters: size - number of values to be assigned.
C++ vector assign() 使用方法及示例
C++ vector assign() 使用方法及示例. C++ Vector(容器) 此函数为向量（vector）分配新值，并替换旧值。语法. 要为其分配值的向量（vector）v。语法为： v.assign(first,last); v.assign(n,val); 参数（first，last）：它定义了范围。将区间（first,last）的元素赋值到当前的vector容器中。
c++11
1. You can use an initializer list for the constructor. Pertaining to conditional initialization as per your edited question, just initialize the vector contents to 0 and then apply whatever condition (s) you require and initialize specific values accordingly: class C. {. public: vector<int> v; C() : v{0,0,0,0}
vector<...>::assign() method
std::vector assign () method. Replaces the contents of the container with the contents of another. (1) Replaces the contents with count copies of value value. (2) Replaces the contents with copies of those in the range [ first, last ).
std::vector::assign
Learn how to assign values to a std::vector container in C++ with examples and explanations from cppreference.com, a reliable source of programming documentation.
How to Assign a std::vector Using a C-Style Array?
To assign a C-Style Array to std::vector, we can use the std::vector::assign () function that replaces the old values of the vector and assigns them the new values. We need to pass the starting and ending address of the array to the function as the argument. C++ Program to Assign Vector using C-Style Array. If we want to insert elements after ...
c++
6. Assign means replacing a vector with new properties (size and elements). Resize means holding old data and expanding the new vector with new elements, this in case the new size is greater than the old one, otherwise shrink the size and eliminate the extra. Run the following code twice. One for assign the second one for resize (just uncomment ...
C++ Vector Library
The C++ function std::vector::assign() assign new values to the vector elements by replacing old ones. It modifies size of vector if necessary. If memory allocation happens allocation is allocated by internal allocator. Declaration. Following is the declaration for std::vector::assign() function form std::vector header.
vector
Any elements held in the container before the call are either assigned to or destroyed. Parameters x A vector object of the same type (i.e., with the same template parameters, T and Alloc). il An initializer_list object. The compiler will automatically construct such objects from initializer list declarators. Member type value_type is the type of the elements in the container, defined in ...
vector::assign() function with example in C++ STL
C++ STL vector::assign() function: Here, we are going to learn about the assign() function of vector header in C++ STL with example. Submitted by IncludeHelp, on May 15, 2019 . C++ vector::assign() function. vector::assign() is a library function of "vector" header, it is used to initialize a vector or assign content to a vector, it assigns the new content to the vector, update the existing ...
vector::assign
Assign vector content Assigns new contents to the vector , replacing its current contents, and modifying its size accordingly. In the range version (1), the new contents are elements constructed from each of the elements in the range between first and last , in the same order.
vectorのresizeとassignの違い #C++
c++のvectorではresizeとassignという機能があります。僕は今までresizeではサイズの指定だけ、assignはサイズと中身、とイメージしていたんですがresizeでも要素を指定できることを知ったので忘れないために違いを書いておこうと思います。 ※簡単のためstd::を省略しています。
Ways to copy a vector in C++
Method 1: Iterative method. This method is a general method to copy, in this method a loop is used to push_back () the old vector elements into the new vector. They are deeply copied. In the above code, changing the value at one vector did not alter the value at another vector, hence they are not allocated at the same address, hence deep copy.
c++
1. The problem is that your operator= only works on individual elements, not on whole vectors. You need to define a constructor that converts an A into a B. Then you can use std::vector::assign rather than std::vector::operator=. int x, y; A(): x(0), y(0) {} A(int x, int y): x(x), y(y) {} int x, y;
c++
myVector[x] = o does something completely different from using myVector.push_back(o) (or using insert).Therefore which method is correct depends on what you are trying to do: myVector[x] = o doesn't insert in the vector, but replaces the element at position x with o.Therefore the length of the vector doesn't change and the value which was previously at position x isn't in the vector any more.
vector::operator= and vector::operator [ ] in C++ STL
1. It is used to assign new contents to the container and replace its current contents. It is used to assign new contents to the container by replacing its current contents. 2. Its syntax is -: vector& operator= (const vector& x); Its syntax is -: vector& operator= (const vector& x); 3.
How to Add Element to Vector of Pairs in C++?
Adding to a Vector of Pairs in C++. We can add an element to a vector of pairs using the vector::std::push_back () function that will append the pair passed inside the function at the end of the vector i.e. after its current last element. Syntax to Add Element to Vector of Pairs in C++. vectorName.push_back({element1, element2}); // or more ...

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[ edit ] Parameters

[ edit ] See also

C++ 数组 & 字符串

C++ vector assign() 使用方法及示例

std::vector assign() method

Parameters ​

Return value ​

Exceptions ​

std::vector:: assign

[ edit ] Parameters

[ edit ] Example

[ edit ] See also

C++ Vector Library - assign() Function

Declaration

Return value

Time complexity

Containers:

Input/Output:

Multi-threading:

member functions

non-member overloads

std:: vector ::operator=

vector::assign() function with example in C++ STL

C++ vector::assign() function

C++ program to demonstrate example of vector::assign() function

<vector>

Containers:

Input/Output:

Multi-threading:

member functions:

non-member overloads:

vectorのresizeとassignの違い

How to Add Element to Vector of Pairs in C++?

Adding to a Vector of Pairs in C++

Syntax to Add Element to Vector of Pairs in C++

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