CODEWITHSUNDEEP
c++c++11vector
CSY
CSY

Reputation: 543

How to find a vector in a 2D vectors in C++?

I'm trying to implement a function to find a vector in a 2D vector. What i have wrote is:

vector<vector<int> > result;
vector<int> line;
bool isPresent = find(result.begin(), result.end(), line)

However, this gives an error that

"Line 11: cannot convert ‘__gnu_cxx::__normal_iterator*, std::vector > >’ to ‘bool’ in initialization"

I searched many forums but couldn't find the right answer. What is the best way to do that?

Thanks, Shawn

Upvotes: 4

Views: 10649

Answers (4)

Piotr Skotnicki
Piotr Skotnicki

Reputation: 48447

InputIterator std::find(InputIterator first, InputIterator last, const T& val)

Returns an iterator to the first element in the range [first,last) that compares equal to val. If no such element is found, the function returns last.

Instead use:

bool isPresent = std::find(result.begin(), result.end(), line) != result.end();
//                                                             ^^^^^^^^^^^^^^^

or:

bool isPresent = std::any_of(result.begin(), result.end(),
                             [&line](const std::vector<int>& x)
                             { return x == line; });

Upvotes: 9

NetVipeC
NetVipeC

Reputation: 4432

Change by:

bool isPresent = (find(result.begin(), result.end(), line) != result.end());

Or Better if C++11 allowed:

bool isPresent = (find(cbegin(result), cend(result), line) != cend(result));

The method std::find of the containers return an iterator of the element that match or the range end (last in the signature method) provided if the element is not present.

template <class InputIterator, class T>
InputIterator find (InputIterator first, InputIterator last, const T& val);

Upvotes: 3

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

Change your code to 

bool isPresent = find(result.begin(), result.end(), line) != result.end();

That should work as you want it. As mentioned std::find() returns a vector<vector<int> >::iterator, not a bool.

Upvotes: 1

Kashyap
Kashyap

Reputation: 17411

My first guess would be find returns the iterator where it found the item you asked it to find and not a boolean.

It should look like this:

vector<vector<int> > result;
vector<int> line;
vector< vector<int> >::iterator it = find(result.begin(), result.end(), line);
bool isPresent = ( it != result.end() );

Upvotes: 1

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