comparison of external value in count_if

Question

I want to iterate through a vector and want to get count of greater elements in another vector. I tried below code snippet, unfortunately it does not work this way.

sort(begin(vec1),end(vec1));
sort(begin(vec2),end(vec2));

for(int i = 0; i < vec1.size(); i++)
{
    int val = vec1[i];
    count_if(begin(vec2),end(vec2),[](int x) { return (x > val); });
}

Answer 1

If you want to count how many elements in vec2 is greater than the i'th element in vec1 then you are doing it correct and just have to capture val in the lambda

for(int i = 0; i < vec1.size(); i++)
{
    int val = vec1[i];
    auto res = count_if(begin(vec2),end(vec2), [val](int x) { return (x > val); });
}

but if you want to compare each element in vec2 with the corresponding element in vec1 you have to do it manually.

int count = 0;
//here the sizes of vec1 and vec2 must be equal
for (auto it1 = begin(vec1), it2 = begin(vec2); it1 != end(vec1); ++it1, ++it2) {
    if (*it2 > *it1)
        ++count;
}

EDIT: As @Jarod42 commented. It is possible to use an algorithm for the second case

auto res = std::transform_reduce(begin(vec2), end(vec2), begin(vec1), 0,
    std::plus<>(), std::greater<>());