You want to build a house on an empty land which reaches all buildings in the shortest amount of distance. You can only move up, down, left and right. You are given a 2D grid of values 0, 1 or 2, where: Each 0 marks an empty land which you can pass by freely. Each 1 marks a building which you cannot pass through. Each 2 marks an obstacle which you cannot pass through.
Given a non-empty array of numbers, a0, a1, a2, … , an-1, where 0 ≤ ai< 231. Find the maximum result of ai XOR aj, where 0 ≤ i, j < n. Could you do this in O(n) runtime? Example Input: [3, 10, 5, 25, 2, 8] Output: 28 Explanation: The maximum result is 5 ^ 25 = 28. Solution (prefix hashset - less efficient) Time: O(N) Space: O(1) class Solution: def findMaximumXOR(self, nums: List[int]) -> int: # 0bxxxxxx - 0b L = len(bin(max(nums))) - 2 max_xor = 0 for i in range(L-1, -1, -1): max_xor <<= 1 print("max_xor:", bin(max_xor) ) # set the rightmost bit to 1 curr_xor = max_xor | 1 print("curr_xor:", bin(curr_xor) ) # highest (L-i) bits prefixes = {num >> i for num in nums} print("prefixes:", [bin(p) for p in prefixes] ) # as long as there exists a p that makes curr_xor^p > 0 # Update max_xor, if two of these prefixes could result in curr_xor.
A car travels from a starting position to a destination which is target miles east of the starting position. Along the way, there are gas stations. Each station[i] represents a gas station that is station[i][0] miles east of the starting position, and has station[i][1] liters of gas. The car starts with an infinite tank of gas, which initially has startFuel liters of fuel in it. It uses 1 liter of gas per 1 mile that it drives.
In facebook, there is a follow table with two columns: followee, follower. Please write a sql query to get the amount of each follower’s follower if he/she has one. For example: +-------------+------------+ | followee | follower | +-------------+------------+ | A | B | | B | C | | B | D | | D | E | +-------------+------------+ should output: +-------------+------------+ | follower | num | +-------------+------------+ | B | 2 | | D | 1 | +-------------+------------+ Explaination: Both B and D exist in the follower list, when as a followee, B's follower is C and D, and D's follower is E.
Table: Queue +-------------+---------+ | Column Name | Type | +-------------+---------+ | person_id | int | | person_name | varchar | | weight | int | | turn | int | +-------------+---------+ person_id is the primary key column for this table. This table has the information about all people waiting for an elevator. The person_id and turn columns will contain all numbers from 1 to n, where n is the number of rows in the table.
Table: Movies +---------------+---------+ | Column Name | Type | +---------------+---------+ | movie_id | int | | title | varchar | +---------------+---------+ movie_id is the primary key for this table. title is the name of the movie. Table: Users +---------------+---------+ | Column Name | Type | +---------------+---------+ | user_id | int | | name | varchar | +---------------+---------+ user_id is the primary key for this table. Table: Movie_Rating +---------------+---------+ | Column Name | Type | +---------------+---------+ | movie_id | int | | user_id | int | | rating | int | | created_at | date | +---------------+---------+ (movie_id, user_id) is the primary key for this table.
Design a HashMap without using any built-in hash table libraries. To be specific, your design should include these functions: put(key, value): Insert a (key, value) pair into the HashMap. If the value already exists in the HashMap, update the value. get(key): Returns the value to which the specified key is mapped, or -1 if this map contains no mapping for the key. remove(key): Remove the mapping for the value key if this map contains the mapping for the key.
Design your implementation of the circular double-ended queue (deque). Your implementation should support following operations: MyCircularDeque(k): Constructor, set the size of the deque to be k. insertFront(): Adds an item at the front of Deque. Return true if the operation is successful. insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful. deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
Solution (Union) SELECT t.team_id, t.team_name, IFNULL(SUM(p.points), 0) AS num_points FROM Teams t LEFT JOIN ( SELECT host_team as team_id, CASE WHEN host_goals > guest_goals THEN 3 WHEN host_goals = guest_goals THEN 1 ELSE 0 END as points FROM Matches UNION ALL SELECT guest_team as team_id, CASE WHEN host_goals < guest_goals THEN 3 WHEN host_goals = guest_goals THEN 1 ELSE 0 END as points FROM Matches ) AS p ON t.team_id = p.
Design a HashSet without using any built-in hash table libraries. To be specific, your design should include these functions: add(value): Insert a value into the HashSet. contains(value): Return whether the value exists in the HashSet or not. remove(value): Remove a value in the HashSet. If the value does not exist in the HashSet, do nothing. Example MyHashSet hashSet = new MyHashSet(); hashSet.add(1); hashSet.add(2); hashSet.contains(1); // returns true hashSet.contains(3); // returns false (not found) hashSet.