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## LeetCode 999. Available Captures for Rook (Java版; Easy)

#### 题目描述

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'

#### 第一次做; 找到白车R, 然后分四次向四个方向探测

class Solution {

public int numRookCaptures(char[][] board) {

int m = board.length, n = board[0].length;

int[][] moves = {{-1,0}, {1,0}, {0,-1}, {0,1}};

int res = 0;

for(int i=0; i<m; i++){

for(int j=0; j<n; j++){

if(board[i][j]=='R'){

for(int[] move : moves){

int x=i, y=j;

x += move[0];

y += move[1];

while(x>=0&&x<m&y>=0&&y<n){

if(board[x][y] == 'B'){

break;

}

if(board[x][y] == 'p'){

res++;

break;

}

x += move[0];

y += move[1];

}

}

return res;

}

}

}

return res;

}

}