Implement matrix transpose and KV store

The phone screen for a Linux-oriented software engineering role included multiple coding tasks: 1. **Transpose an `n x n` matrix** Given a square matrix of size `n x n`, transform it so that rows become columns. In other words, return the matrix transpose, where `result[i][j] = matrix[j][i]`. 2. **Design an object-oriented key-value store with `set`, `get`, and `setAll`** Implement a key-value store supporting the following operations: - `set(key, value)`: assign `value` to `key` - `get(key)`: return the current value for `key`, or indicate that the key does not exist - `setAll(value)`: update all existing keys so that they now return `value` The design should be object-oriented. Discuss the expected time complexity of each operation, and implement the API efficiently. A separate prompt mentioned reviewing a short C snippet and identifying bugs or issues, but the code itself was not provided, so that part is omitted here.