How to find out if an item is present in a std::vector?
You can use std::find
from <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 a bool (true
if present, false
otherwise). With your example:
#include <algorithm>
#include <vector>
if ( std::find(vec.begin(), vec.end(), item) != vec.end() )
do_this();
else
do_that();
As others have said, use the STL find
or find_if
functions. But if you are searching in very large vectors and this impacts performance, you may want to sort your vector and then use the binary_search
, lower_bound
, or upper_bound
algorithms.
Use find from the algorithm header of stl.I've illustrated its use with int type. You can use any type you like as long as you can compare for equality (overload == if you need to for your custom class).
#include <algorithm>
#include <vector>
using namespace std;
int main()
{
typedef vector<int> IntContainer;
typedef IntContainer::iterator IntIterator;
IntContainer vw;
//...
// find 5
IntIterator i = find(vw.begin(), vw.end(), 5);
if (i != vw.end()) {
// found it
} else {
// doesn't exist
}
return 0;
}