Count closed islands in a grid

## Problem You are given an `m x n` 2D grid representing a map after flooding: - `0` = water - `1` = land An **island** is a maximal 4-directionally connected component of land cells (`1`s), where connectivity is via **up, down, left, right** (not diagonals). A **closed island** is an island that **does not touch the grid boundary** (i.e., none of its cells lie in the first/last row or first/last column). Any island that touches the boundary is **not counted**. ### Task Return the number of **closed islands** in the grid. ### Input - `grid`: `int[m][n]` ### Output - `int`: the number of closed islands ### Notes / Assumptions - Use 4-directional adjacency. - You may assume `m, n >= 1`. ### Example If an island is entirely surrounded by water but a land cell touches the border, it should **not** be counted as closed.