I have vector of strings, and I need to check if the array contains duplicates:
std::vector<std::string> data{};
const bool notContainsDuplicates = ...;
Can I solve this problem with standard library?
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2Can I solve this problem with standard library? Probably yes, but not sure what is your end goal or actual requirement.kiner_shah– kiner_shah2022-01-26 14:22:44 +00:00Commented Jan 26, 2022 at 14:22
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Can you sort the vector (or a copy of the vector) first? That would make the job a lot easier.catnip– catnip2022-01-26 14:24:49 +00:00Commented Jan 26, 2022 at 14:24
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2Does this answer your question? More elegant way to check for duplicates in C++ array?kiner_shah– kiner_shah2022-01-26 14:25:01 +00:00Commented Jan 26, 2022 at 14:25
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I can't sort and change vectorQuickDzen– QuickDzen2022-01-26 14:28:58 +00:00Commented Jan 26, 2022 at 14:28
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My -1 for you not explaining the problem.user1196549– user11965492022-01-26 15:16:17 +00:00Commented Jan 26, 2022 at 15:16
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1 Answer
You can do it like this, using a standard library set to count the number of unique entries, if this is the same as the length of the input array there are no duplicates (another option is to use an unordered_map) :
#include <cassert>
#include <string>
#include <string_view> // edit : added
#include <vector>
#include <set>
bool contains_duplicates(const std::vector<std::string>& input)
{
// edit removed : std::set<std::string> set{ input.begin(), input.end() };
std::set<std::string_view> set{ input.begin(), input.end() };
return (set.size() != input.size());
}
int main()
{
std::vector<std::string> no_dups{ "hello","this","does","not","contain","duplicates" };
std::vector<std::string> dups{ "hello","this","does","contain","duplicates","hello","this" };
assert(!contains_duplicates(no_dups));
assert(contains_duplicates(dups));
return 0;
}
4 Comments
Alan Birtles
std::set<std::string_view> would avoid copying the strings
PaulMcKenzie
You could reduce the function to a single line:
return std::set<std::string_view>(input.begin(), input.end()).size() != input.size();
Pepijn Kramer
@AlanBirtles A thanks for that feedback didn't think of that. But it sure would be an improvement.
Pepijn Kramer
Edit : Added the string_view solution
