How should I practice Count Connected Islands?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Twitch onsite interview problems in FastPrep.

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Problem · Array

Count Connected Islands

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Problem statement

You are given a rectangular binary grid encoded as an array of equal-length strings. Character 1 represents land and character 0 represents water.

An island is a maximal group of land cells connected through shared edges. Cells that touch only at a corner are not connected.

Return the number of islands. Do not modify the input grid.

Function

countIslands(grid: String[]) → int

Examples

Example 1

grid = ["110","010","101"]return = 3

The three connected components are the upper-left group, the land cell at the lower left, and the land cell at the lower right.

Example 2

grid = ["0000","0000"]return = 0

Every cell is water, so the grid contains no island.

Constraints

1 <= grid.length <= 500
1 <= grid[i].length <= 500
All rows have the same length.
Every character is 0 or 1.
grid.length * grid[i].length <= 2 * 10^5