Compute max reachable cells per threshold

You are given:

• An m x n integer matrix terrain .
• An integer array limits of length k .

For each query value L = limits[i], you start at the top-left cell (0, 0) and may move repeatedly to any 4-directionally adjacent cell (up/down/left/right).

Rules for scoring and movement:

• You are allowed to step onto a cell (r, c) only if L is strictly greater than terrain[r][c] .
• The first time you visit an allowed cell, you gain 1 point .
• You may revisit cells any number of times, but you do not gain additional points for revisits.
• The process effectively ends when no additional moves to allowed (unvisited or visited) cells are possible under the rule above.

Define answer[i] as the maximum number of points you can obtain for limits[i].

Return the array answer.

Function signature

• Input: int[][] terrain, int[] limits
• Output: int[] answer

Example 1

terrain = [
  [1, 4, 2, 8],
  [0, 4, 0, 8],
  [1, 2, 0, 8]
]
limits = [8, 2]
answer = [9, 3]

Example 2

terrain = [
  [2, 5, 7],
  [3, 5, 1]
]
limits = [5, 6, 2]
answer = [5, 8, 1]

Notes:

• You should aim for an efficient solution when k is large (many queries).
• terrain values may repeat; limits are arbitrary integers.