How to make numpy.argmax return all occurrences of the maximum?

Question

I\'m trying to find a function that returns all occurrences of the maximum in a given list.

numpy.argmax however only returns the first occurrence that it f

Answer 1

In case it matters, the following algorithm runs in O(n) instead of O(2n) (i.e., using np.argmax and then np.argwhere):

def allmax(a):
    if len(a) == 0:
        return []
    all_ = [0]
    max_ = a[0]
    for i in range(1, len(a)):
        if a[i] > max_:
            all_ = [i]
            max_ = a[i]
        elif a[i] == max_:
            all_.append(i)
    return all_