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Number Of Islands

Count how many separate islands of land exist in a 2D grid.

Acceptance 100%
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Problem Statement

You are given a 2D grid of characters where each cell is either land ('1') or water ('0'). An island is a group of land cells connected horizontally or vertically. Diagonal adjacency does not count.

Return the number of distinct islands in the grid.

Input Format

  • A 2D grid of characters or binary values.
  • Each cell represents either land or water.
  • Cells are connected only in the four cardinal directions.

Output Format

  • Return a single integer: the number of connected groups of land cells.

Constraints

  • Connectivity is 4-directional only.
  • You may assume the grid has at least one row and one column.
  • A cell belongs to exactly one island or to water.
Examples
Sample cases returned by the problem API.

Example 1

Input

grid = [
  ['1','1','0','0','0'],
  ['1','1','0','0','0'],
  ['0','0','1','0','0'],
  ['0','0','0','1','1']
]

Output

3

Explanation

There are three separate islands: one in the top-left, one in the middle, and one in the bottom-right.

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