蓄水池抽样

蓄水池抽样

def reservoir_sampling(vec, k):
    if k >= len(vec):
        return vec
    arr = vec[:k]
    for i, e in enumerate(vec[k:]):
        r = np.random.randint(0, k + i + 1)
        if r <= k-1:
            arr[r] = e
    return sorted(arr)