How to find an object in table C++

Question

i have function which finds a number in a table:

int find(int arrf[], int len, int seek)
{
    for (int i = 0; i < len; ++i)
        if (arrf[i] == seek) 
            return i;
    return -1;
}

Is there a faster way to do this?

Can you sort the array first - or update it to use std::vector? — UKMonkey, Dec 06 '17 at 16:24
Why would there be ? No magic in computers, you have to search one by one... — kebs, Dec 06 '17 at 16:25
@Karol Borecki It is the linear search. If the array is not sorted then there is no other methods. On the other hand the function implementation is bad. There is already standard algorithm std::find in C++. — Vlad from Moscow, Dec 06 '17 at 16:26
related: https://stackoverflow.com/questions/249392/binary-search-in-array — UKMonkey, Dec 06 '17 at 16:33
@Karol Borecki The function declaration should look at least like size_t find( const int a[], size_t n, int x ); — Vlad from Moscow, Dec 06 '17 at 16:37
@pm100 it doesn't help the issue of searching for an item; it helps on # of arguments to the function, maintainability, memory management, abstraction (potentially). — UKMonkey, Dec 06 '17 at 16:43
No i cant sort this first, thanks guys a lot, i just want to make sure this is the best way. — Karol Borecki, Dec 06 '17 at 17:52

score 0 · Answer 1 · answered Dec 06 '17 at 17:27

For linear search two optimizations come to mind:

Build a vectorized implementation that uses SIMD instructions to do multiple comparisons at the same time.
Parallelize search to multiple CPUs. That only makes sense if the array to search is sufficiently large to warrant multi-threading overhead.

Intel Parallel STL can do both optimizations for you.

1 Answers1