#Reservoir Sampling : large and unknown size
# Definition for singly-linked list.
# class ListNode(object):
# def __init__(self, x):
# self.val = x
# self.next = None
from random import randint
class Solution(object):
def __init__(self, head):
"""
@param head The linked list's head.
Note that the head is guaranteed to be not null, so it contains at least one node.
:type head: ListNode
"""
self.__head=head
def getRandom(self):
"""
Returns a random node's value.
:rtype: int
"""
reservoir=self.__head.val
curr,n=self.__head.next,1
while curr:
if randint(1,n+1)==1:
reservoir=curr.val
curr,n=curr.next,n+1
return reservoir
# Your Solution object will be instantiated and called as such:
# obj = Solution(head)
# param_1 = obj.getRandom()
382. Linked List Random Node
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