comparing implementations of 'is x in a set of numbers' - https://godbolt.org/z/9en4qv

containers-are-expensive.cpp

int baseline(int x)
{
    switch (x)
    {
        case 0:
        case 2:
        case 8:
        case 15:
        case 16:
            return 5;
    }
    return x * x;
}

#include <array>
#include <algorithm>
int usinglist(int x)
{
    const std::array<int, 5> s = {
        0, 2, 8, 15, 16
    };

    if (std::any_of(s.begin(), s.end(),
        [x](int n){ return n == x; }))
        return 5;
    
    return x * x;
}

#include <set>
int usingset(int x)
{
    const std::set<int> s = {
        0, 2, 8, 15, 16
    };

    if (s.count(x))
        return 5;
    
    return x * x;
}