Pawns the Rook Can Take

Easy

You are given an 8 × 8 chessboard as a list of rows board. It holds exactly one white rook 'R', some white bishops 'B' and some black pawns 'p'; empty squares are '.'. The rook moves in a straight line, up, down, left or right, any number of squares, but it cannot jump over pieces: its path ends at the first occupied square or at the edge of the board. A pawn is under attack if the rook can land on its square in one move, which means the pawn is the first piece in one of the four directions. Return how many pawns the rook is attacking right now.

Example 1

board=[[".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", "p", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", "p", "B", ".", "R", ".", "p", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", "B", ".", ".", "."], [".", ".", ".", ".", "p", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."]] → 2

The rook is at row 3, column 4. Upward there is a pawn, and to the right there is a pawn. To the left a bishop comes first and shields the pawn behind it; downward there is a bishop too. The answer is 2.

Example 2

board=[["R", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], ["p", "p", ".", ".", ".", ".", ".", "."]] → 1

The rook sits in a corner. The pawn in the bottom-left corner shares its column with nothing in between; the other pawn is off the rook's lines. The answer is 1.

Constraints

board has 8 rows of 8 squares
every square is 'R', 'B', 'p' or '.'
there is exactly one rook 'R'

Have you seen this problem in a real interview?

Solved by0

Tried by0

Submissions0

Acceptance—

Topics

Array Matrix Simulation

Similar problems

Repack the Tray Easy Mirror and Negate a Bitmap Easy Swap Rows and Columns Easy Rolling Grid Easy Noughts and Crosses Verdict Easy

Input

board=[[".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", "p", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", "p", "B", ".", "R", ".", "p", "."], [".", ".", ".", ".", ".", ".", ".", "."], [".", ".", ".", ".", "B", ".", ".", "."], [".", ".", ".", ".", "p", ".", ".", "."], [".", ".", ".", ".", ".", ".", ".", "."]]

Expected

Run checks the first 3 tests in your browser. Submit checks all 60 tests on the server, hidden ones included.