Island areas and water boundaries

You are given an m x n grid of characters. Each cell is '1' (land) or '0' (water). Land cells that share a side (up, down, left or right) belong to the same island. Diagonal cells are not connected.

For every island, report two numbers:

• Area: how many land cells the island has.
• Water boundary: how many cell sides of the island touch water. Treat everything outside the grid as water, so a land side on the edge of the map counts. A side shared by two land cells of the island does not count.

Implement island_stats(grid) -> list[tuple[int, int]], returning one (area, boundary) pair per island. List islands in the order a row-by-row, left-to-right scan first reaches them. The number of islands is the length of the result.

Constraints

• 0 <= m, n <= 1000
• Each cell is '0' or '1'.
• Aim for O(m * n) time. Your solution must not fail on a grid that is entirely land.

Example 1

grid = ["1100",
        "1001",
        "0011"]

Output: [(3, 8), (3, 8)]. The top-left island has 3 cells and 8 sides that face water or the map edge. The bottom-right island also has 3 cells and 8 such sides.

Example 2

grid = ["111",
        "101",
        "111"]

Output: [(8, 16)]. The ring has 12 sides on the outside and 4 sides around the water cell in the middle.

Reconstructed from the reported question; details may differ from what interviewers ask.