check if a std::vector contains a certain object?
Checking if v
contains the element x
:
#include <algorithm>
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()...
.
See question: How to find an item in a std::vector?
You'll also need to ensure you've implemented a suitable operator==()
for your object, if the default one isn't sufficient for a "deep" equality test.