c std vector assignment operator

<cassert> (assert.h)
<cctype> (ctype.h)
<cerrno> (errno.h)
C++11 <cfenv> (fenv.h)
<cfloat> (float.h)
C++11 <cinttypes> (inttypes.h)
<ciso646> (iso646.h)
<climits> (limits.h)
<clocale> (locale.h)
<cmath> (math.h)
<csetjmp> (setjmp.h)
<csignal> (signal.h)
<cstdarg> (stdarg.h)
C++11 <cstdbool> (stdbool.h)
<cstddef> (stddef.h)
C++11 <cstdint> (stdint.h)
<cstdio> (stdio.h)
<cstdlib> (stdlib.h)
<cstring> (string.h)
C++11 <ctgmath> (tgmath.h)
<ctime> (time.h)
C++11 <cuchar> (uchar.h)
<cwchar> (wchar.h)
<cwctype> (wctype.h)

Containers:

C++11 <array>
<deque>
C++11 <forward_list>
<list>
<map>
<queue>
<set>
<stack>
C++11 <unordered_map>
C++11 <unordered_set>
<vector>

Input/Output:

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

Multi-threading:

C++11 <atomic>
C++11 <condition_variable>
C++11 <future>
C++11 <mutex>
C++11 <thread>
<algorithm>
<bitset>
C++11 <chrono>
C++11 <codecvt>
<complex>
<exception>
<functional>
C++11 <initializer_list>
<iterator>
<limits>
<locale>
<memory>
<new>
<numeric>
C++11 <random>
C++11 <ratio>
C++11 <regex>
<stdexcept>
<string>
C++11 <system_error>
C++11 <tuple>
C++11 <type_traits>
C++11 <typeindex>
<typeinfo>
<utility>
<valarray>
vector<bool>
vector::~vector
vector::vector

member functions

vector::assign
vector::back
vector::begin
vector::capacity
C++11 vector::cbegin
C++11 vector::cend
vector::clear
C++11 vector::crbegin
C++11 vector::crend
C++11 vector::data
C++11 vector::emplace
C++11 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
C++11 vector::shrink_to_fit
vector::size
vector::swap

non-member overloads

relational operators (vector)
swap (vector)

std:: vector ::operator=

Return value, iterator validity, exception safety.

Standard Template Library
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STL Interview Questions
STL Cheatsheet
C++ Templates
C++ Functors
C++ Iterators

vector::operator= and vector::operator[ ] in C++ STL

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.

This operator is used to assign new contents to the container by replacing the existing contents. It also modifies the size according to the new contents.

Syntax :

Examples:

Errors and Exceptions 1. If the containers are of different types, an error is thrown. 2. It has a basic no exception throw guarantee otherwise.

Time Complexity – Linear O(N)

Output:

This operator is used to reference the element present at position given inside the operator. It is similar to the at() function, the only difference is that the at() function throws an out-of-range exception when the position is not in the bounds of the size of vector, while this operator causes undefined behavior .

Syntax :

Examples:

Errors and Exceptions 1. If the position is not present in the vector, it shows undefined behavior. 2. It has a no exception throw guarantee otherwise.

Time Complexity – Constant O(1)

Application Given a vector of integers, print all the integers present at odd positions.

Algorithm 1. Run a loop till the size of the vector. 2. Check if the position is not divisible by 2, then print the element at that position.

Let us see the differences in a tabular form -:

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cppreference.com

Std:: vector.

The elements are stored contiguously, which means that elements can be accessed not only through iterators, but also using offsets to regular pointers to elements. This means that a pointer to an element of a vector may be passed to any function that expects a pointer to an element of an array.

The storage of the vector is handled automatically, being expanded as needed. Vectors usually occupy more space than static arrays, because more memory is allocated to handle future growth. This way a vector does not need to reallocate each time an element is inserted, but only when the additional memory is exhausted. The total amount of allocated memory can be queried using capacity() function. Extra memory can be returned to the system via a call to shrink_to_fit() [1] .

Reallocations are usually costly operations in terms of performance. The reserve() function can be used to eliminate reallocations if the number of elements is known beforehand.

The complexity (efficiency) of common operations on vectors is as follows:

Random access - constant 𝓞(1) .
Insertion or removal of elements at the end - amortized constant 𝓞(1) .
Insertion or removal of elements - linear in the distance to the end of the vector 𝓞(n) .

std::vector (for T other than bool ) meets the requirements of Container , AllocatorAwareContainer (since C++11) , SequenceContainer , ContiguousContainer (since C++17) and ReversibleContainer .