Count Enclosed Land Regions (Medium) — Practice with Code Visualizer

You are given a two-dimensional binary matrix representing a geographical map where each cell contains either a 0 (representing land) or a 1 (representing water).

A land region is defined as a group of adjacent land cells (value 0) that are connected horizontally or vertically (4-directional connectivity). Two cells are considered part of the same land region if you can travel between them by moving only through adjacent land cells.

An enclosed land region is a land region that is completely surrounded by water on all sides. More specifically, a land region is considered enclosed if and only if:

No cell in the region touches the boundary (edge) of the grid
Every cell in the region has water cells or other land cells (that are also completely enclosed) in all four cardinal directions when traced to the grid boundary

Your task is to count and return the total number of distinct enclosed land regions in the given grid.

Key Observations:

Land cells on the boundary of the grid (first row, last row, first column, or last column) cannot be part of an enclosed region
Any land region that contains at least one boundary-touching cell is NOT enclosed
Water cells (1s) act as barriers that can fully surround land regions

The grid contains two enclosed land regions. The first enclosed region is the connected group of 0s in rows 1-3, columns 1-4 (a roughly rectangular shape). The second enclosed region is the single 0 cell at row 2, column 3 which sits inside the first region but is separated by water. The 0s touching the right edge of the grid are NOT enclosed because they connect to the boundary.

There is exactly one enclosed land region: the single 0 cell at position (1,2) which is completely surrounded by water cells (1s). All other 0 cells in the grid touch the boundary edges, so they cannot form enclosed regions.

This grid features a 'nested' structure. The outer ring of 0s forms one enclosed region. Inside that ring, there is a smaller enclosed region consisting of the single 0 cell at position (3,3). The water cells create concentric barriers that separate these two distinct enclosed land regions.