Easy
On an 8 x 8
chessboard, there is exactly one white rook 'R'
and some number of white bishops 'B'
, black pawns 'p'
, and empty squares '.'
.
When the rook moves, it chooses one of four cardinal directions (north, east, south, or west), then moves in that direction until it chooses to stop, reaches the edge of the board, captures a black pawn, or is blocked by a white bishop. A rook is considered attacking a pawn if the rook can capture the pawn on the rook’s turn. The number of available captures for the white rook is the number of pawns that the rook is attacking.
Return the number of available captures for the white rook.
Example 1:
Input: board = [[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”p”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”R”,”.”,”.”,”.”,”p”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”p”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”]]
Output: 3
Explanation: In this example, the rook is attacking all the pawns.
Example 2:
Input: board = [[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”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: The bishops are blocking the rook from attacking any of the pawns.
Example 3:
Input: board = [[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”p”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”p”,”.”,”.”,”.”,”.”],[“p”,”p”,”.”,”R”,”.”,”p”,”B”,”.”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”B”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”p”,”.”,”.”,”.”,”.”],[”.”,”.”,”.”,”.”,”.”,”.”,”.”,”.”]]
Output: 3
Explanation: The rook is attacking the pawns at positions b5, d6, and f5.
Constraints:
board.length == 8
board[i].length == 8
board[i][j]
is either 'R'
, '.'
, 'B'
, or 'p'
board[i][j] == 'R'
class Solution {
fun numRookCaptures(board: Array<CharArray>): Int {
// Find the position of the rook
var rookRow = -1
var rookCol = -1
for (i in 0..7) {
for (j in 0..7) {
if (board[i][j] == 'R') {
rookRow = i
rookCol = j
break
}
}
if (rookRow != -1) {
break
}
}
// Define the four directions: up, right, down, left
val directions = arrayOf<IntArray>( // up
intArrayOf(-1, 0), // right
intArrayOf(0, 1), // down
intArrayOf(1, 0), // left
intArrayOf(0, -1),
)
var captureCount = 0
// Check each direction
for (dir in directions) {
var row = rookRow
var col = rookCol
while (true) {
// Move one step in the current direction
row += dir[0]
col += dir[1]
// Check if out of bounds
if (row < 0 || row >= 8 || col < 0 || col >= 8) {
break
}
// If we hit a bishop, we're blocked
if (board[row][col] == 'B') {
break
}
// If we hit a pawn, we can capture it and then we're blocked
if (board[row][col] == 'p') {
captureCount++
break
}
// Otherwise (empty square), continue in the same direction
}
}
return captureCount
}
}