999. Available Captures for Rook

Author: YuriSpiridonov

Easy/999.AvailableCapturesforRook.py

@@ -0,0 +1,87 @@
+"""
+    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:
+    Input: [[".",".",".",".",".",".",".","."],
+            [".",".",".","p",".",".",".","."],
+            [".",".",".","R",".",".",".","p"],
+            [".",".",".",".",".",".",".","."],
+            [".",".",".",".",".",".",".","."],
+            [".",".",".","p",".",".",".","."],
+            [".",".",".",".",".",".",".","."],
+            [".",".",".",".",".",".",".","."]]
+    Output: 3
+    Explanation: 
+                 In this example the rook is able to capture all the pawns.
+
+    Example:
+    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:
+    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:
+        1. board.length == board[i].length == 8
+        2. board[i][j] is either 'R', '.', 'B', or 'p'
+        3. There is exactly one cell with board[i][j] == 'R'
+"""
+#Difficulty: Easy
+#22 / 22 test cases passed.
+#Runtime: 40 ms
+#Memory Usage: 14.2 MB
+
+#Runtime: 40 ms, faster than 6.85% of Python3 online submissions for Available Captures for Rook.
+#Memory Usage: 14.1 MB, less than 44.63% of Python3 online submissions for Available Captures for Rook.
+
+class Solution:
+    def numRookCaptures(self, board: List[List[str]]) -> int:
+        pawns = 0
+        for i in range(8):
+            if 'R' in board[i]:
+                j = board[i].index('R')
+                vert = [board[i][j] for i in range(8)]
+                pawns += self.counter(board[i][:j][::-1])
+                pawns += self.counter(board[i][j+1:])
+                pawns += self.counter(vert[:i][::-1])
+                pawns += self.counter(vert[i+1:])
+                break
+        return pawns
+
+    def counter(self, line):
+        for char in line:
+            if char == 'p':
+                return 1
+            if char == 'B':
+                break
+        return 0