CODEWITHSUNDEEP
c++searchvector
3bdalla
3bdalla

Reputation: 407

Efficient way to search a vector of structs for a specific ID?

I have a vector of structs Data which has an integer data member ID. I need to search if it contains an instance of a specific ID. I had to do it this way:

int DataSize = 0;
for(unsigned count = 0; count < Data.size(); count++)
{
    if(ID == Data[count].ID)
        DataSize++;
}

Where ID is previously defined. Any more efficient way to search a vector of objects ? Especially when it is a part of an embedded application.

Upvotes: 0

Views: 221

Answers (2)

NetVipeC
NetVipeC

Reputation: 4432

With C++11 and lambdas could write a little more expresive as:

If you want to count the struct with ID:

std::count_if(std::cbegin(dataArray), std::cend(dataArray), [ID](const Data& data) {
    return data.ID == ID;
});

If you want to known if there is at least one:

bool found_ID = std::cend(dataArray) != std::find_if(std::cbegin(dataArray), std::cend(dataArray), [ID](const Data& data) {
    return data.ID == ID;
});

The other algorithms of the STD it's always good to have at hand, some are used only very few time, but could save a lot of debugging (with edge case) and performance problems if implemented by hand.

Upvotes: 1

Pradhan
Pradhan

Reputation: 16737

Use std::count_if.

std::count_if(Data.begin(), Data.end(), [&ID](const DataType& data){return ID == data.ID; };

where DataType is the type of elements contained in Data.

Note that there are no real efficiency gains to be had unless Data satisfied some more conditions, for example, being sorted by ID. However, using a standard algorithm improves readability.

Upvotes: 1

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