367. Valid Perfect Square
Reservioir Sampling, Linked List, Math, Randomized ·Problem Statement
link: LeetCode.cn LeetCode
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.
Implement the Solution class:
Solution(ListNode head) Initializes the object with the head of the singly-linked list head. int getRandom() Chooses a node randomly from the list and returns its value. All the nodes of the list should be equally likely to be chosen.
Example:
Input: ["Solution", "getRandom", "getRandom", "getRandom", "getRandom", "getRandom"][[[1, 2, 3]], [], [], [], [], []]
Output: [null, 1, 3, 2, 2, 3]
Solution Approach
Algorithm
Implement
class Solution:
def isPerfectSquare(self, num: int) -> bool:
l, r = 0, num
while l <= r:
m = (l + r) // 2
t = m * m
if t == nums:
return True
if t < num:
l = m + 1
else:
r = m - 1
return False