leetcode之Linked List Random Node

这题本身来讲是比较简单的。把所有的值放进一个list里，想取哪个取哪个。

import random
# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

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.list1 = []
        while head:
            self.list1.append(head.val)
            head = head.next


    def getRandom(self):
        """
        Returns a random node's value.
        :rtype: int
        """
        location = random.randint(1, len(self.list1))
        return self.list1[location - 1]

但是这样是要花费额外时间的，如果按照题目要求的那样，不花费额外的话，做法就相当于每个node都roll个点，roll完一遍之后，谁的点大谁就胜出。