Re: Comparing Multiple Strings More Efficiently
Brad <email@example.com> wrote in news:52e2672c-7517-4429-88a9-
I think there are better (more efficient) ways to do this, but I've
only ever needed this simple approach:
void compare(const std::vector<std::string>& strings)
// Normally, this is randomly generated. It is a C style
char the_string = "abc";
for (std::vector<std::string>::const_iterator sit = strings.begin
sit != send; ++sit)
if (the_string == *sit)
std::clog << "MATCH:\t" << *sit << std::endl;
Basically, I'm comparing a randomly generated string to a vector of
strings by iterating through the vector (as seen above). Here is the
problem: The vector may have one or millions of strings and execution
time slows considerably when I go above a few thousand strings.
Is there a more efficient way to approach this? My code works fine on
smaller vectors, I just never expected to do millions and it may not
be possible to do that many as quickly as a few, but I wanted to ask.
Perhaps there is something in algorithm that I could use. Just point
me to it. I prefer standard C++ wherever possible.
If the vector of strings is more or less constant during the program
life-time, then you can keep it sorted (see std::sort()) and use
std::binary_search() or std::lower_bound() instead of the loop.
If the vector frequently changes, then you can use std::set<std::string>
instead, which keeps the strings sorted all the time automatically, and
use the find() member function of std::set() for lookup.
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