Vector size() in C++ STL

In C++, the vector size() is a built-in method used to find the size of a vector. The size of a vector tells us the number of elements currently present in the vector. In this article, we will learn about the vector size() method.

Let's take a look at the simple code example:

5

Explanation: The number of elements in the vector v is 5, which is returned by the vector size() function.

Syntax of Vector size()

The vector size() method is the member function of std::vector defined inside <vector> header file.

v.size();

This function does not take any parameters.

Return Value

• Returns the number of elements in the vector as size_t value.
• If the vector is empty, returns 0.

Example of Vector size()

The vector size() is a very simple and easy to use function. The code examples below show how to use this function:

Find the Number of Elements in Vector

2
5

Check if Vector is Empty

The size() method can be used to check whether a vector is empty by comparing its size to zero.

Empty.

Traverse the Vector Using Index and size()

1 2 3 5 4 

Vector size() vs capacity()

The vector size() returns the number of elements currently stored in the vector while vector capacity() returns the total number of elements the vector can hold before needing to reallocate memory.