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Takefumi Yamamura's blog

This blog is for my memorandum.

Takefumi Yamamura's b!og

This blog is for my memorandum

200. Number of Islands(Leet Code, Google)


Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by water.

Example 1:

11110 11010 11000 00000 Answer: 1

Example 2:

11000 11000 00100 00011 Answer: 3

How to Solve

To solve this, I used bfs search. Firstly, I check the each coordinate. If I didn't visit that coordinate I starts to bfs search from it and I change the visited flag true. The number of this times if the answer.