check if a std::vector contains a certain object? [duplicate]

Question

Is there something in <algorithm> which allows you to check if a std:: container contains something? Or, a way to make one, for example:

if(a.x == b.x && a.y == b.y) return true;  return false; 

Can this only be done with std::map since it uses keys?

Thanks

Answer 1

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 */ } 

Answer 2

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()....