C++ STL: Push Back Array into Container

Pushing the elements of an array into the back of a STL container, in a single statement, is easy using the STL std::copy algorithm. This algorithm relies on the destination having enough space to hold the source elements. So, a convenient way to apply it on a container without allocating the required space is to use a std::back_inserter. This works on all containers that have a push_back method: vector, list and deque.

#include <algorithm>
#include <iterator>
std::copy( fooArray, fooArray + ARRAY_SIZE, std::back_inserter( fooVector ) );

C++: Set Array Using STL

A common initialization or cleanup operation when using arrays is set all its elements to a common value. It is typically done as:

for (int i = 0; i < SIZE; ++i)
    arr[i] = VAL;

The STL algorithm std::fill can be used to achieve the same with a single statement:

#include <algorithm>
std::fill( arr, arr + SIZE, VAL );

C++ STL: Copy vector to array

The array behaves like a vector and so can be used almost everywhere a vector is used. So, a vector can be copied into an array using std::copy algorithm. But, make sure that the array is big enough to hold the elements of the vector when you do this:

#include <vector>

std::vector<Foo> fooVec;
Foo fooArr[FOO_MAX];

std::copy( fooVec.begin(), fooVec.end(), fooArr );

C++: Initialize STL Vector with Array

A STL vector does not have any constructor that looks like it accepts an array. So, the straightforward way to initialize a vector with an array looks like:

#include <vector>

int arr[ARR_LEN] = { /* Array elements */ };
std::vector iVec;
for (int i = 0; i < ARR_LEN; ++i)
    iVec.push_back( arr[i] );

That is too much code for a simple initialization! Thankfully, there is another way do it with less code.

The constructor vector(InputIterator begin, InputIterator end) which initializes a vector with the elements of the range [begin, end) can be used with arrays too. This is because array pointers have all the properties required of an (input) iterator:

#include <vector>

int arr[ARR_LEN] = { /* Array elements */ };
std::vector<int> iVec(arr, arr + ARR_LEN);

Note that the second argument arr + ARR_LEN is beyond the last element of the array and thus behaves as the correct end().