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Implement 2048 Game Logic | Glean Interview Question

Q: Implement 2048 Game Logic

This question evaluates array and matrix manipulation, stateful simulation of game mechanics, and handling edge cases such as merge constraints, single-merge-per-move rules, and empty-cell management.

Implement the core logic for the 2048 game.

You are given an n x n integer board where 0 represents an empty cell and every nonzero value represents a tile value. Implement a method such as move(direction) that updates the board after one move in one of four directions: up, down, left, or right.

Rules:

All tiles slide as far as possible in the chosen direction.
Adjacent tiles with the same value merge into one tile with double the value.
A tile may participate in at most one merge per move.
Empty cells are filled with 0 after sliding and merging.
You do not need to implement the UI. If random new-tile generation is needed, keep it separate from the deterministic movement logic.

Examples for a left move on a single row:

[2, 0, 2, 0] -> [4, 0, 0, 0]
[2, 2, 2, 0] -> [4, 2, 0, 0]
[2, 2, 2, 2] -> [4, 4, 0, 0]

Follow-up: implement isGameOver(), which returns true if no legal move remains. A game is over when the board has no empty cells and there are no horizontally or vertically adjacent equal tiles.