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Number of Islands

Google● MediumINTERNFULLTIMENEW GRADPHONE SCREENONSITE INTERVIEW

Problem statement

You are given an m x n grid of characters. A cell containing '1' is land and a cell containing '0' is water.

An island is a maximal group of land cells connected horizontally or vertically. Treat the area outside all four grid edges as water.

The problem statement continues

Pro

Examples

Example 1

grid = [["1","1","1","1","0"],["1","1","0","1","0"],["1","1","0","0","0"],["0","0","0","0","0"]]return = 1

Every land cell belongs to one four-directionally connected component.

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