std::vector<T,Allocator>::operator[]

reference operator[]( size_type pos );
const_reference operator[]( size_type pos ) const;

Returns a reference to the element at specified location pos. No bounds checking is performed.

Parameters

pos

position of the element to return

Return value

Reference to the requested element.

Complexity

Constant.

Notes

Unlike std::map::operator[], this operator never inserts a new element into the container.

Example

The following code uses operator[] to read from and write to a std::vector<int>:

#include <vector>
#include <iostream>
 
int main()
{
    std::vector<int> numbers {2, 4, 6, 8};
 
    std::cout << "Second element: " << numbers[1] << '\n';
 
    numbers[0] = 5;
 
    std::cout << "All numbers:";
    for (auto i : numbers) {
        std::cout << ' ' << i;
    }
    std::cout << '\n';
}

Output:

Second element: 4
All numbers: 5 4 6 8