string::find_last_not_of (2 of 2 overloads)

Find the last occurrence of a character not equal to ch.

std::size_t
find_last_not_of(
    char ch,
    std::size_t pos = string::npos) const noexcept;

Returns the index corrosponding to the last character of {begin(), begin() + pos} that is not equal to ch if it exists, and npos otherwise.

Linear.

The last occurrence of a character that is not equal to ch before or at the index pos, or npos if none exists.

Name	Description
`ch`	The character to ignore.
`pos`	The index to start searching at. The default argument for this parameter is `npos`.

Boost C++ Libraries