CODEWITHSUNDEEP
c++std
Administrator
Administrator

Reputation: 270

Is there a function like find_last_of in std but not in string?

I know there is function

string::find_last_of

But I want to process a large chunk of char* data. I don't want to assign the char* to a string.

I know there is a std function

std::find

But it only can find char* on positive sequence. Is there such a way to find in reverse order? If not in std, is there a way in boost?

Upvotes: 2

Views: 1304

Answers (4)

fir las
fir las

Reputation: 84

For single-character searching, there is std::ranges::find_last now (unfortunately only in C++23; and there is no std::find_last counterpart)

https://en.cppreference.com/w/cpp/algorithm/ranges/find_last

Example:

#include<algorithm>
#include<vector>
#include<cassert>

...

std::vector<char> str{ '1','2','2','3','4' };
auto find = std::ranges::find_last(str.begin(), str.end(), '2'); // [last '2', str.end())
assert(find.begin() == str.begin() + 2 && find.end() == str.end());

Upvotes: 0

bolov
bolov

Reputation: 75815

If you want to search for one character, like std::find() does, you can use... std::find(). Take a look at std::reverse_iterator:

auto foo(char* str, std::size_t size, char to_find)
{
    auto rev_it = std::find(std::make_reverse_iterator(str + size),
                            std::make_reverse_iterator(str),
                            to_find);
    auto it = std::make_reverse_iterator(rev_it);

}

Upvotes: 2

Administrator
Administrator

Reputation: 270

There is a function in boost can solve this problem.

boost::algorithm::find_last

example:

char* s = "abcdabc";
cout << boost::algorithm::find_last(s, "b").begin() - s;

Upvotes: 1

Remy Lebeau
Remy Lebeau

Reputation: 597051

std::find_end()

Searches for the last subsequence of elements [s_first, s_last) in the range [first, last).

For example

#include <algorithm>

char *data = ...;
char *data_end = data + size;
char toFind = ...;
char *pfind = &toFind;

char *found = std::find_end(data, data_end, pfind, pfind + 1);
if (found != data_end)
    ...

Upvotes: 3

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