In C++ check if std::vector<string> contains a certain value [duplicate]

Question

This question already has an answer here:

• How to find out if an item is present in a std::vector? 18 answers

Is there any built in function which tells me that my vector contains a certain element or not e.g.

std::vector<string> v;
v.push_back("abc");
v.push_back("xyz");

if (v.contains("abc")) // I am looking for one such feature, is there any
                       // such function or i need to loop through whole vector?

Answer 1

You can use std::find as follows:

if (std::find(v.begin(), v.end(), "abc") != v.end())
{
  // Element in vector.
}

To be able to use std::find: include <algorithm>.

Answer 2

1. If your container only contains unique values, consider using std::set instead. It allows querying of set membership with logarithmic complexity.

   std::set<std::string> s;
   s.insert("abc");
   s.insert("xyz");
   if (s.find("abc") != s.end()) { ...
   

2. If your vector is kept sorted, use std::binary_search, it offers logarithmic complexity as well.

3. If all else fails, fall back to std::find, which is a simple linear search.

Answer 3

In C++11, you can use std::any_of instead.

An example to find if there is any zero in the array:

std::array<int,3> foo = {0,1,-1};
if ( std::any_of(foo.begin(), foo.end(), [](int i){return i==0;}) )
std::cout << "zero found...";

Answer 4

it's in <algorithm> and called std::find.

Answer 5

std::find().