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Understanding the Functionality of std::remove
In C , the std::remove algorithm operates on an arbitrary sequence represented by two forward iterators. Its purpose is to rearrange elements within the sequence, moving non-matching elements forward. Unlike std::erase, remove does not physically delete elements from the container. Instead, it reorganizes them.
Example
Consider the following code snippet:
std::vector<int> a; a.push_back(1); a.push_back(2); std::remove(a.begin(), a.end(), 1); std::vector<int>::iterator iter = a.begin(); std::vector<int>::iterator endIter = a.end(); std::cout << "Using iter...\n"; for (; iter != endIter; ++iter) { std::cout << *iter << "\n"; } std::cout << "Using size...\n"; for (int i = 0; i < a.size(); ++i) { std::cout << a[i] << "\n"; }
The output will be:
Using iter... 2 2 Using size... 2 2
Although remove has effectively moved the element 2 forward, the vector's size remains unchanged at 2 because the uninitialized memory has not been removed.
Erase-Remove Idiom
The erase-remove idiom combines remove and erase to physically remove unwanted elements. The code:
a.erase(std::remove(a.begin(), a.end(), 1), a.end());
would remove the element 1 from the vector and reduce its size to 1.
Use Cases of std::remove
While the primary use of remove is in the erase-remove idiom, it can also be utilized in other situations, such as:
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