999 Available Captures for Rook py3

999 Available Captures for Rook.py

@@ -0,0 +1,51 @@
+#!/usr/bin/python3
+"""
+On an 8 x 8 chessboard, there is one white rook.
+There also may be empty squares, white bishops, and black pawns.
+These are given as characters 'R', '.', 'B', and 'p' respectively.
+Uppercase characters represent white pieces, and lowercase characters represent black pieces.
+
+The rook moves as in the rules of Chess:
+it chooses one of four cardinal directions (north, east, west, and south),
+then moves in that direction until it chooses to stop, reaches the edge of the board,
+or captures an opposite colored pawn by moving to the same square it occupies.
+Also, rooks cannot move into the same square as other friendly bishops.
+
+Return the number of pawns the rook can capture in one move.
+
+Example 1:
+Input: [[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".","R",".",".",".","p"],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."]]
+Output: 3
+Explanation: In this example the rook is able to capture all the pawns.
+
+Example 2:
+Input: [[".",".",".",".",".",".",".","."],[".","p","p","p","p","p",".","."],[".","p","p","B","p","p",".","."],[".","p","B","R","B","p",".","."],[".","p","p","B","p","p",".","."],[".","p","p","p","p","p",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".",".",".",".","."]]
+Output: 0
+Explanation: Bishops are blocking the rook to capture any pawn.
+
+Example 3:
+Input: [[".",".",".",".",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".","p",".",".",".","."],["p","p",".","R",".","p","B","."],[".",".",".",".",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","p",".",".",".","."],[".",".",".",".",".",".",".","."]]
+Output: 3
+Explanation: The rook can capture the pawns at positions b5, d6 and f5.
+
+Note:
+board.length == board[i].length == 8
+board[i][j] is either 'R', '.', 'B', or 'p'
+There is exactly one cell with board[i][j] == 'R'
+"""
+
+class Solution:
+    def numRookCaptures(self, board):
+        for i in range(8):
+            for j in range(8):
+                if board[i][j] == 'R':
+                    x0, y0 = i, j
+        res = 0
+        for i, j in [[1, 0], [0, 1], [-1, 0], [0, -1]]:
+            x, y = x0 + i, y0 + j
+            while 0 <= x < 8 and 0 <= y < 8:
+                if board[x][y] == 'p': res += 1
+                if board[x][y] != '.': break
+                x, y = x + i, y + j
+        return res
+