Is There Any pop_front Method in C++ std::vector?
No is the quick answer to this query. Vectors do not have a built-in pop_front method in the C++ standard library, unlike other container classes like deque and list. The fundamental design principle of vectors, which promotes quick random access to elements, is the cause of this absence. The removal of the first element necessitates a shift of all succeeding components since vectors store their elements in a contiguous memory block.
It is essential to look into pop_back in order to get why pop_front is unavailable in std::vector. A common vector method called pop_back eliminates the final component of the container. This is accomplished by executing the destructor of the member that was removed and lowering the vector’s size by one. As vectors expand from their back, eliminating the final component is a simple operation that doesn’t involve relocating any other elements. Yet, eliminating the initial element would cause all subsequent components to move one space to the left. Since this procedure copies every vector element, it is incredibly inefficient, especially for big vectors. The pop_front is therefore excluded from std::vector in order to prevent vector operations from being slowed down.
Alternatives of pop_front Method in C++
There are numerous ways to remove components from the front of a vector despite the lack of a pop_front method.
1: Erase Method
One technique is to utilize the erase method on the vector’s initial element. The erase method modifies the remaining components to reflect the removal of an element or set of items from the vector. Thus, we can use the following line of code in C++ to achieve the same behavior as pop_front:
#include <vector>
template<typename T>
void pop_front(std::vector<T> &v)
{
if (v.size() > 0) {
v.erase(v.begin());
}
}
int main()
{
std::vector<int> nums = { 5,6,7,8,9 };
pop_front(nums);
for (int i: nums) {
std::cout << i << ' ';
}
return 0;
}
In the above code, we are using the erase() function as an alternative of pop_front() to remove the first element of a vector initialized. We have defined a function named pop_front(), and in the function, we are using the begin() and erase() functions to remove the first element of the vector.
Output
2: Deque Method
Another container in the C++ Standard Library is the deque, which offers the capability of a dynamic array-like container with the added ability to add and remove elements from both the front and the back. Using a deque (double-ended queue) in place of a vector is an additional substitute for pop_front. So, we can use it to achieve the same behavior as pop_front:
#include <deque>
using namespace std;
int main()
{
deque<int> mydeque;
mydeque.push_front(4);
mydeque.push_front(5);
mydeque.push_front(6);
mydeque.pop_front();
for (auto it = mydeque.begin(); it != mydeque.end(); ++it)
cout << ' ' << *it;
}
In the above code, we are using a push_front() function to push the values in a deque, and a pop_front() function to remove the first element from the deque.
Output
Conclusion
Due to its internal memory structure and design principles, std::vector in C++ does not have a pop_front method. There are, however, several additional techniques, such as the use of deque and erase methods that can be used to remove elements from the front of the container. When selecting the best approach for their implementation, programmers must compromise between convenience and efficiency.
