You know how to count islands. You have the scan-and-sink pattern locked in: outer loop finds the next '1', launches DFS, DFS sinks the entire connected region, count increments. Clean and fast.
Now the question changes. Not “how many islands?” but “which island is biggest?” Before you answer — look at this grid. Three islands. Island A sprawls in an L shape. Island B connects through two cells. Island C sits alone. Which one has the most cells?
Tap an island to find out its area. Your eyes have an opinion. The algorithm has the truth. They are not always the same.