ChiPy Algorithms SIGDescription
Given a singly linked list, return a random node’s value from the linked list. Each node must have the same probability of being chosen.
Follow up: What if the linked list is extremely large and its length is unknown to you? Could you solve this efficiently without using extra space?
Solution
Other solutions can be found on the problem source link at the top of the post.
class ReservoirSampling(object):
def __init__(self, max_size):
self.reservoir = []
self.max = max_size
self.i = 0
def add(self, element):
size = len(self.reservoir)
if size >= self.max:
spot = random.randint(0, self.i - 1)
if spot < size:
self.reservoir[spot] = element
else:
self.reservoir.append(element)
self.i += 1