Solve Two Grid Search Problems

Solve the following two coding problems. 1. **Count disconnected land regions** - You are given an `m x n` grid of characters where `'1'` represents land and `'0'` represents water. - A region is formed by connecting land cells horizontally or vertically. - Return the number of distinct land regions in the grid. 2. **Compute infection time in a grid** - You are given an `m x n` grid where: - `0` = empty cell - `1` = fresh item - `2` = infected item - Every minute, each infected item spreads infection to its adjacent fresh items in the four cardinal directions. - Return the minimum number of minutes required until no fresh item remains. - If it is impossible to infect all fresh items, return `-1`. The interview note suggests medium-to-upper-medium difficulty and primarily tests graph traversal on grids, especially DFS, BFS, and multi-source BFS.