(This question has been seen in the interviews of the following companies: Google)
Given a binary grid where 0 represents water and 1 represents land. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. Delete all islands except their borders. A border is land adjacent to water. You may assume all four edges of the grid are surrounded by water.
Example 1:
Input:
[[0, 0, 0, 1, 1, 1],
[0, 0, 0, 1, 1, 1],
[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1]]
Output:
[[0, 0, 0, 1, 1, 1],
[0, 0, 0, 1, 0, 1],
[1, 1, 1, 1, 0, 1],
[1, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1]]
Input:
[[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1],
[1, 1, 1, 1, 1, 1]]
Output:
[[1, 1, 1, 1, 1, 1],
[1, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 1],
[1, 0, 0, 0, 0, 1],
[1, 1, 1, 1, 1, 1]]
Input:
[[1, 1, 1, 0, 1, 1, 1],
[1, 1, 1, 0, 1, 1, 1],
[1, 1, 1, 0, 1, 1, 1],
[0, 0, 0, 0, 1, 1, 1],
[1, 1, 1, 0, 1, 1, 1]]
Output:
[[1, 1, 1, 0, 1, 1, 1],
[1, 0, 1, 0, 1, 0, 1],
[1, 1, 1, 0, 1, 0, 1],
[0, 0, 0, 0, 1, 0, 1],
[1, 1, 1, 0, 1, 1, 1]]
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