1958-CheckIfMoveIsLegal.go

package main

// 1958. Check if Move is Legal
// You are given a 0-indexed 8 x 8 grid board, where board[r][c] represents the cell (r, c) on a game board. 
// On the board, free cells are represented by '.', white cells are represented by 'W', and black cells are represented by 'B'.

// Each move in this game consists of choosing a free cell and changing it to the color you are playing as (either white or black). 
// However, a move is only legal if, after changing it, the cell becomes the endpoint of a good line (horizontal, vertical, or diagonal).

// A good line is a line of three or more cells (including the endpoints) where the endpoints of the line are one color, 
// and the remaining cells in the middle are the opposite color (no cells in the line are free). 
// You can find examples for good lines in the figure below:
//     <img src="https://assets.leetcode.com/uploads/2021/07/22/goodlines5.png" />

// Given two integers rMove and cMove and a character color representing the color you are playing as (white or black), 
// return true if changing cell (rMove, cMove) to color color is a legal move, or false if it is not legal.

// Example 1:
// <img src="https://assets.leetcode.com/uploads/2021/07/10/grid11.png" />
// Input: board = [[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],["W","B","B",".","W","W","W","B"],[".",".",".","B",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."]], rMove = 4, cMove = 3, color = "B"
// Output: true
// Explanation: '.', 'W', and 'B' are represented by the colors blue, white, and black respectively, and cell (rMove, cMove) is marked with an 'X'.
// The two good lines with the chosen cell as an endpoint are annotated above with the red rectangles.

// Example 2:
// <img src="https://assets.leetcode.com/uploads/2021/07/10/grid2.png" />
// Input: board = [[".",".",".",".",".",".",".","."],[".","B",".",".","W",".",".","."],[".",".","W",".",".",".",".","."],[".",".",".","W","B",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".","B","W",".","."],[".",".",".",".",".",".","W","."],[".",".",".",".",".",".",".","B"]], rMove = 4, cMove = 4, color = "W"
// Output: false
// Explanation: While there are good lines with the chosen cell as a middle cell, there are no good lines with the chosen cell as an endpoint.

// Constraints:
//     board.length == board[r].length == 8
//     0 <= rMove, cMove < 8
//     board[rMove][cMove] == '.'
//     color is either 'B' or 'W'.

import "fmt"

func checkMove(board [][]byte, rMove int, cMove int, color byte) bool {
    direction := [][]int{{1, 0}, {-1, 0}, {0, 1}, {0, -1}, {1, 1}, {-1, -1}, {1, -1}, {-1, 1}}
    var  dfs func(board [][]byte, r int, c int, color byte, direcn []int, length int) bool
    dfs = func (board [][]byte, r int, c int, color byte, direcn []int, length int) bool {
        nr, nc := r + direcn[0], c + direcn[1]
        if nr < 0 || nc < 0 || nr >= len(board) || nc >= len(board[0]) { // 边界检测
            return false
        }
        if board[nr][nc] == color {
            if length >= 2 {
                return true
            } else {
                return false
            }
        } else {
            if board[nr][nc] == '.' {
                return false
            }
            return dfs(board, nr, nc, color, direcn, length+1)
        }
    }
    for _, d := range direction {
        if dfs(board, rMove, cMove, color, d, 1) {
            return true
        }
    }
    return false
}

func main() {
    // Example 1:
    // <img src="https://assets.leetcode.com/uploads/2021/07/10/grid11.png" />
    // Input: board = [[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],[".",".",".","W",".",".",".","."],["W","B","B",".","W","W","W","B"],[".",".",".","B",".",".",".","."],[".",".",".","B",".",".",".","."],[".",".",".","W",".",".",".","."]], rMove = 4, cMove = 3, color = "B"
    // Output: true
    // Explanation: '.', 'W', and 'B' are represented by the colors blue, white, and black respectively, and cell (rMove, cMove) is marked with an 'X'.
    // The two good lines with the chosen cell as an endpoint are annotated above with the red rectangles.
    board1 := [][]byte{
        {'.','.','.','B','.','.','.','.'},
        {'.','.','.','W','.','.','.','.'},
        {'.','.','.','W','.','.','.','.'},
        {'.','.','.','W','.','.','.','.'},
        {'W','B','B','.','W','W','W','B'},
        {'.','.','.','B','.','.','.','.'},
        {'.','.','.','B','.','.','.','.'},
        {'.','.','.','W','.','.','.','.'},
    }
    fmt.Println(checkMove(board1, 4, 3, 'B')) // true
    // Example 2:
    // <img src="https://assets.leetcode.com/uploads/2021/07/10/grid2.png" />
    // Input: board = [[".",".",".",".",".",".",".","."],[".","B",".",".","W",".",".","."],[".",".","W",".",".",".",".","."],[".",".",".","W","B",".",".","."],[".",".",".",".",".",".",".","."],[".",".",".",".","B","W",".","."],[".",".",".",".",".",".","W","."],[".",".",".",".",".",".",".","B"]], rMove = 4, cMove = 4, color = "W"
    // Output: false
    // Explanation: While there are good lines with the chosen cell as a middle cell, there are no good lines with the chosen cell as an endpoint.
    board2 := [][]byte{
        {'.','.','.','.','.','.','.','.'},
        {'.','B','.','.','W','.','.','.'},
        {'.','.','W','.','.','.','.','.'},
        {'.','.','.','W','B','.','.','.'},
        {'.','.','.','.','.','.','.','.'},
        {'.','.','.','.','B','W','.','.'},
        {'.','.','.','.','.','.','W','.'},
        {'.','.','.','.','.','.','.','B'},
    }
    fmt.Println(checkMove(board2, 4, 4, 'W')) // false
}