Code RoomCount islands
MediumPrep Room Coding #1566

Count islands

CodingAlgorithms & data structuresMid–Senior~30 min

Given a grid of 1s (land) and 0s (water), count the number of islands. An island is a group of 1s connected horizontally or vertically.

Implement
num_islands(grid: list[list[int]]) → int
Examples
in[[[1,1,0],[1,0,0],[0,0,1]]]out2
What a strong answer looks like

State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.

0:00 of about 30 min
InputExpectedGot
[[[1,1,0],[1,0,0],[0,0,1]]]2not run yetsample