curriculum/challenges/english/blocks/rosetta-code-challenges/5e4ce2f5ac708cc68c1df261.md
A linear congruential generator (LCG) is an <em>algorithm</em> that yields a sequence of pseudo-randomized numbers calculated with a discontinuous piecewise linear equation. All linear congruential generators use this formula:
$$r_{n + 1} = (a \times r_n + c) \bmod m$$
Where:
<ul> <li>$ r_0 $ is a seed.</li> <li>$r_1$, $r_2$, $r_3$, ..., are the random numbers.</li> <li>$a$, $c$, $m$ are constants.</li> </ul>If one chooses the values of $a$, $c$ and $m$ with care, then the generator produces a uniform distribution of integers from $0$ to $m - 1$.
<abbr title="linear congruential generator">LCG</abbr> numbers have poor quality. $r_n$ and $r_{n + 1}$ are not independent, as true random numbers would be. Anyone who knows $r_n$ can predict $r_{n + 1}$, therefore <abbr title="linear congruential generator">LCG</abbr> is not cryptographically secure. The <abbr title="linear congruential generator">LCG</abbr> is still good enough for simple tasks like Miller-Rabin primality test, or FreeCell deals. Among the benefits of the <abbr title="linear congruential generator">LCG</abbr>, one can easily reproduce a sequence of numbers, from the same $r_0$. One can also reproduce such sequence with a different programming language, because the formula is so simple.
Write a function that takes $r_0,a,c,m,n$ as parameters and returns $r_n$.
linearCongGenerator should be a function.
assert(typeof linearCongGenerator == 'function');
linearCongGenerator(324, 1145, 177, 2148, 3) should return a number.
assert(typeof linearCongGenerator(324, 1145, 177, 2148, 3) == 'number');
linearCongGenerator(324, 1145, 177, 2148, 3) should return 855.
assert.equal(linearCongGenerator(324, 1145, 177, 2148, 3), 855);
linearCongGenerator(234, 11245, 145, 83648, 4) should return 1110.
assert.equal(linearCongGenerator(234, 11245, 145, 83648, 4), 1110);
linearCongGenerator(85, 11, 1234, 214748, 5) should return 62217.
assert.equal(linearCongGenerator(85, 11, 1234, 214748, 5), 62217);
linearCongGenerator(0, 1103515245, 12345, 2147483648, 1) should return 12345.
assert.equal(linearCongGenerator(0, 1103515245, 12345, 2147483648, 1), 12345);
linearCongGenerator(0, 1103515245, 12345, 2147483648, 2) should return 1406932606.
assert.equal(
linearCongGenerator(0, 1103515245, 12345, 2147483648, 2),
1406932606
);
function linearCongGenerator(r0, a, c, m, n) {
}
function linearCongGenerator(r0, a, c, m, n) {
for (let i = 0; i < n; i++) {
r0 = (a * r0 + c) % m;
}
return r0;
}