pub fn max_by<T>(
v: &mut [T],
n: usize,
cmp: impl FnMut(&T, &T) -> Ordering
) -> &mut [T]
Get the n largest items with a comparator function.
This function is stable, i.e. it preserves the order of equal elements.
Panics if n > len.
let mut v = [-5, 4, 1, -3, 2];
let min = out::max_by(&mut v, 3, |a, b| b.cmp(a));
assert_eq!(min, [1, -3, -5]);