Check if one string is a prefix of another

c++ string-comparison prefix
fredley picture fredley · Oct 27, 2011 · Viewed 45.5k times · Source

I have two strings which I'd like to compare: String and String:. Is there a library function that would return true when passed these two strings, but false for say String and OtherString?

To be precise, I want to know whether one string is a prefix of another.

Answer

Nim picture Nim · Oct 27, 2011

Use std::mismatch. Pass in the shorter string as the first iterator range and the longer as the second iterator range. The return is a pair of iterators, the first is the iterator in the first range and the second, in the second rage. If the first is end of the first range, then you know the the short string is the prefix of the longer string e.g.

std::string foo("foo");
std::string foobar("foobar");

auto res = std::mismatch(foo.begin(), foo.end(), foobar.begin());

if (res.first == foo.end())
{
  // foo is a prefix of foobar.
}

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