for j := i; j > a && (cmp(data[j], data[j-1]) < 0); j-- {
			data[j], data[j-1] = data[j-1], data[j]
		}
	}
}

// siftDownCmpFunc implements the heap property on data[lo:hi].
// first is an offset into the array where the root of the heap lies.
func siftDownCmpFunc[E any](data []E, lo, hi, first int, cmp func(a, b E) int) {
	root := lo
	for {
		child := 2*root + 1
		if child >= hi {
			break
		}