Solve grid path and top‑k frequency

Part A — Grid Reachability with Obstacles: Given an m×n matrix of 0s and 1s where 0 indicates a passable cell and 1 indicates a blocked cell, starting at (0, 0) determine whether there exists a path to the bottom-right cell (m−1,n− 1). You may move up, down, left, or right within bounds and cannot enter blocked cells. Return true if such a path exists, otherwise false.

Part B — Top‑K Frequent Numbers: Given an array of integers and an integer k, return the k numbers that appear most frequently in the array. If multiple numbers have the same frequency, any order among them is acceptable.