Two Pointer Technique

a popular programming technique used to solve problems involving arrays or lists efficiently. It involves using two pointers (or indices) to traverse the data structure and is commonly used in problems related to searching, sorting, and subarray operations. It Typically can reduces the time complexity from $O(n^2)$ to $O(n)$ for many problems. - ChatGPT

Example

std::unique

template<class ForwardIt>
ForwardIt unique(ForwardIt first, ForwardIt last)
{
    if (first == last)
        return last;
 
    ForwardIt result = first;
    while (++first != last)
        if (!(*result == *first) && ++result != first)
            *result = std::move(*first);
 
    return ++result;
}