Both the match() (returns the first appearance) and %in% (returns a Boolean) functions are designed for this. v <- c(‘a’,’b’,’c’,’e’) ‘b’ %in% v ## returns TRUE match(‘b’,v) ## returns the first location of ‘b’, in this case: 2
To delete a single element, you could do: std::vector<int> vec; vec.push_back(6); vec.push_back(-17); vec.push_back(12); // Deletes the second element (vec[1]) vec.erase(std::next(vec.begin())); Or, to delete more than one element at once: // Deletes the second through third elements (vec[1], vec[2]) vec.erase(std::next(vec.begin(), 1), std::next(vec.begin(), 3));
If your compiler supports C++11, you can simply do: std::vector<int> v = {1, 2, 3, 4}; This is available in GCC as of version 4.4. Unfortunately, VC++ 2010 seems to be lagging behind in this respect. Alternatively, the Boost.Assign library uses non-macro magic to allow the following: #include <boost/assign/list_of.hpp> … std::vector<int> v = boost::assign::list_of(1)(2)(3)(4); Or: … Read more
Vector synchronizes on each individual operation. That’s almost never what you want to do. Generally you want to synchronize a whole sequence of operations. Synchronizing individual operations is both less safe (if you iterate over a Vector, for instance, you still need to take out a lock to avoid anyone else changing the collection at … Read more
You can use std::find from <algorithm>: #include <algorithm> #include <vector> vector<int> vec; //can have other data types instead of int but must same datatype as item std::find(vec.begin(), vec.end(), item) != vec.end() This returns an iterator to the first element found. If not present, it returns an iterator to one-past-the-end. With your example: #include <algorithm> #include … Read more
a.insert(a.end(), b.begin(), b.end()); or a.insert(std::end(a), std::begin(b), std::end(b)); The second variant is a more generically applicable solution, as b could also be an array. However, it requires C++11. If you want to work with user-defined types, use ADL: using std::begin, std::end; a.insert(end(a), begin(b), end(b));
vector1.insert( vector1.end(), vector2.begin(), vector2.end() );