Checking if v contains the element x:
#include
if(std::find(v.begin(), v.end(), x) != v.end()) {
/* v contains x */
} else {
/* v does not contain x */
}
Checking if v contains elements (is non-empty):
if(!v.empty()){
/* v is non-empty */
} else {
/* v is empty */
}
If searching for an element is important, I’d recommend std::set instead of std::vector. Using this:
std::find(vec.begin(), vec.end(), x) runs in O(n) time, but std::set has its own find() member (ie. myset.find(x)) which runs in O(log n) time – that’s much more efficient with large numbers of elements
std::set also guarantees all the added elements are unique, which saves you from having to do anything like if not contained then push_back()….