linkedListRandomNode.py

#! /usr/bin/env python3
# -*- coding: utf-8 -*-

# Source: https://leetcode.com/problems/linked-list-random-node/
# Author: Miao Zhang
# Date:   2021-02-06

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, val=0, next=None):
#         self.val = val
#         self.next = next
class Solution:

    def __init__(self, head: ListNode):
        """
        @param head The linked list's head.
        Note that the head is guaranteed to be not null, so it contains at least one node.
        """
        self.nodes = []
        while head:
            self.nodes.append(head.val)
            head = head.next

    def getRandom(self) -> int:
        """
        Returns a random node's value.
        """
        return self.nodes[random.randint(0, len(self.nodes) - 1)]


# Your Solution object will be instantiated and called as such:
# obj = Solution(head)
# param_1 = obj.getRandom()