Counting similar ints in a vector

Question

Is there a stl function for vector that will allow me to find the number of elements in a vector? For example if I was looking for the count of ints 4 in this vector:

vector<ACard> PairFinder;

for (int i = 0; i < 5; i++)
{
Pairfinder[i] = rand()%5+1
}

Answer 1

You want std::count :

#include <algorithm>

int n = std::count(PairFinder.begin(), PairFinder.end(), 4);

If you cannot easily represent the value type you're looking for, you can use the variant std::count_if to specify a custom predicate.

Answer 2

是的，很容易，使用algorithm标头中的std::count ：

int fours = std::count(PairFinder.begin(), PairFinder.end(), 4);