Solve DFS grid and keypad problems

Q: Solve DFS grid and keypad problems

This question evaluates understanding of DFS and backtracking for grid traversal and combinatorial generation, assessing skills in graph traversal, recursion, connected-component counting, and mapping digit sequences to letter combinations.

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Question

You may be asked to solve one or more DFS/backtracking problems:

Grid connectivity problem : Given an m x n grid where 1 represents land and 0 represents water, count how many connected land regions exist. Cells are connected horizontally and vertically.
Phone keypad combinations : On a classic phone keypad, digits map to letters as follows: 2 -> abc , 3 -> def , 4 -> ghi , 5 -> jkl , 6 -> mno , 7 -> pqrs , 8 -> tuv , 9 -> wxyz .
- Given a digit string such as 2345 , generate all possible letter strings it can represent.
- Also determine how many possible outputs exist for the input.

Explain your approach, edge cases, and time/space complexity.

Solve DFS grid and keypad problems

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