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Number of Islands Mock Interview

  1. ✓Problem→
  2. 2Clarifying Questions→
  3. 3Constraints→
  4. 4Brute Force→
  5. 5Complexity Analysis→
  6. 6Pattern Recognition→
  7. 7Optimized Solution→
  8. 8Implementation→
  9. 9Testing→
  10. 10Follow-Up→
  11. 11Evaluation
Problem

Given an m × n grid of characters where '1' represents land and '0' represents water, return the number of islands. An island is a maximal group of land cells connected horizontally or vertically (not diagonally). You may assume the grid is surrounded by water.

Constraints
  • 1 ≤ m, n ≤ 300
  • grid[i][j] is '0' or '1'
Example
in: grid = [["1","1","0"],["0","1","0"],["0","0","1"]]
out: 2

Clarify

Before choosing anything: what would you ask the interviewer? What assumptions are you making? (Duplicates? Empty input? Value ranges? What to return when there is no answer?)