1500. Design a File Sharing System
We will use a file-sharing system to share a very large file which consists of m small chunks with IDs from 1 to m.
When users join the system, the system should assign a unique ID to them. The unique ID should be used once for each user, but when a user leaves the system, the ID can be reused again.
Users can request a certain chunk of the file, the system should return a list of IDs of all the users who own this chunk. If the user receives a non-empty list of IDs, they receive the requested chunk successfully.
Implement the FileSharing class:
- FileSharing(int m) Initializes the object with a file of m chunks.
- int join(int[] ownedChunks): A new user joined the system owning some chunks of the file, the system should assign an id to the user which is the smallest positive integer not taken by any other user. Return the assigned id.
- void leave(int userID): The user with userID will leave the system, you cannot take file chunks from them anymore.
- int[] request(int userID, int chunkID): The user userID requested the file chunk with chunkID. Return a list of the IDs of all users that own this chunk sorted in ascending order.
1535. Find the Winner of an Array Game
Given an integer array arr of distinct integers and an integer k.
A game will be played between the first two elements of the array (i.e. arr[0] and arr[1]). In each round of the game, we compare arr[0] with arr[1], the larger integer wins and remains at position 0, and the smaller integer moves to the end of the array. The game ends when an integer wins k consecutive rounds.
Return the integer which will win the game.
It is guaranteed that there will be a winner of the game.
1536. Minimum Swaps to Arrange a Binary Grid
Given an n x n binary grid, in one step you can choose two adjacent rows of the grid and swap them.
A grid is said to be valid if all the cells above the main diagonal are zeros.
Return the minimum number of steps needed to make the grid valid, or -1 if the grid cannot be valid.
The main diagonal of a grid is the diagonal that starts at cell (1, 1) and ends at cell (n, n).
1545. Find Kth Bit in Nth Binary String
Given two positive integers n and k, the binary string Sn is formed as follows:
- S1 = “0”
- Si = Si - 1 + “1” + reverse(invert(Si - 1)) for i > 1
Where + denotes the concatenation operation, reverse(x) returns the reversed string x, and invert(x) inverts all the bits in x (0 changes to 1 and 1 changes to 0).
For example, the first four strings in the above sequence are:
- S1 = “0”
- S2 = “011”
- S3 = “0111001”
- S4 = “011100110110001”
Return the kth bit in Sn. It is guaranteed that k is valid for the given n.
1561. Maximum Number of Coins You Can Get
There are 3n piles of coins of varying size, you and your friends will take piles of coins as follows:
- In each step, you will choose any 3 piles of coins (not necessarily consecutive).
- Of your choice, Alice will pick the pile with the maximum number of coins.
- You will pick the next pile with the maximum number of coins.
- Your friend Bob will pick the last pile.
- Repeat until there are no more piles of coins.
Given an array of integers piles where piles[i] is the number of coins in the ith pile.
Return the maximum number of coins that you can have.