Lonely Dark Pixels

Medium

The image picture is a rectangular grid where every cell is either dark ("B") or light ("W"). A dark pixel is lonely when no other dark pixel shares its row or its column. Return the number of lonely dark pixels.

Example 1

picture=[["B", "W", "W"], ["W", "W", "B"], ["W", "W", "B"]] → 1

The corner pixel at (0, 0) is lonely. The two dark pixels in the last column spoil each other.

Example 2

picture=[["W", "B"], ["B", "W"]] → 2

Both dark pixels are alone in their rows and columns.

Constraints

1 ≤ number of rows, number of columns ≤ 500
Every cell is "B" or "W"

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Topics

Array Hash Table Matrix

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Input

picture=[["B", "W", "W"], ["W", "W", "B"], ["W", "W", "B"]]

Expected

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