Function core::slice::select::median_of_medians

fn median_of_medians<T, F: FnMut(&T, &T) -> bool>(
    v: &mut [T],
    is_less: &mut F,
    k: usize
)

Selection algorithm to select the k-th element from the slice in guaranteed O(n) time. This is essentially a quickselect that uses Tukey’s Ninther for pivot selection