very fast factorial function

fast_factorial.c

#include <stdint.h>
#include <stddef.h>

// An uint64_t can't hold more than 18446744073709551616 and 21! is very huge
// just store a table of these values upto 20

static uint64_t factorial_table[21] = {
    1,
    1,
    2,
    6,
    24,
    120,
    720,
    5040,
    40320,
    362880,
    3628800,
    39916800,
    479001600,
    6227020800,
    87178291200,
    1307674368000,
    20922789888000,
    355687428096000,
    6402373705728000,
    121645100408832000,
    2432902008176640000
};

uint64_t factorial_return(int n) {
    if (n > 20 || n < 0)
        return -1; // uint64_t max lmao

    return factorial_table[n];
}

"just use a lookup table itll be faster"