LeetCode 348. Design Tic-Tac-Toe [Swift 题解]

题目

Design a Tic-tac-toe game that is played between two players on a n x n grid.

You may assume the following rules:

A move is guaranteed to be valid and is placed on an empty block.
Once a winning condition is reached, no more moves is allowed.
A player who succeeds in placing n of their marks in a horizontal, vertical, or diagonal row wins the game.
Example:
Given n = 3, assume that player 1 is "X" and player 2 is "O" in the board.

TicTacToe toe = new TicTacToe(3);

toe.move(0, 0, 1); -> Returns 0 (no one wins)  
|X| | |
| | | |    // Player 1 makes a move at (0, 0).
| | | |

toe.move(0, 2, 2); -> Returns 0 (no one wins)  
|X| |O|
| | | |    // Player 2 makes a move at (0, 2).
| | | |

toe.move(2, 2, 1); -> Returns 0 (no one wins)  
|X| |O|
| | | |    // Player 1 makes a move at (2, 2).
| | |X|

toe.move(1, 1, 2); -> Returns 0 (no one wins)  
|X| |O|
| |O| |    // Player 2 makes a move at (1, 1).
| | |X|

toe.move(2, 0, 1); -> Returns 0 (no one wins)  
|X| |O|
| |O| |    // Player 1 makes a move at (2, 0).
|X| |X|

toe.move(1, 0, 2); -> Returns 0 (no one wins)  
|X| |O|
|O|O| |    // Player 2 makes a move at (1, 0).
|X| |X|

toe.move(2, 1, 1); -> Returns 1 (player 1 wins)  
|X| |O|
|O|O| |    // Player 1 makes a move at (2, 1).
|X|X|X|

思路

第一种思路是根据tic tac toe validation那一题的validation function, 每走一步都validate一遍, 这样其实有些浪费,是因为move这个方法调用的时候我们assume它是调用的合理的, 这样其实是没必要做一些count 类似的validation的,而且每走一步我们的rowCount/colCount都是可以随着变化的

Swift 题解

class TicTacToe {

    /** Initialize your data structure here. */
    var rowCount: [Int]
    var colCount: [Int]
    var diagCount: Int
    var antiDiagCount: Int

    var board: [[Int]]

    init(_ n: Int) {
        self.rowCount = Array(repeating: 0, count: n)
        self.colCount = Array(repeating: 0, count: n)
        self.diagCount = 0
        self.antiDiagCount = 0
        self.board = Array(repeating: Array(repeating: 0, count: n), count: n)
    }

    /** Player {player} makes a move at ({row}, {col}).
     @param row The row of the board.
     @param col The column of the board.
     @param player The player, can be either 1 or 2.
     @return The current winning condition, can be either:
     0: No one wins.
     1: Player 1 wins.
     2: Player 2 wins. */
    func move(_ row: Int, _ col: Int, _ player: Int) -> Int {
        let add = player == 1 ? 1 : -1
        rowCount[row] += add
        colCount[col] += add
        if row == col {
            diagCount += add
        }

        let size = rowCount.count

        if (row + col) == (size - 1) {
            antiDiagCount += add
        }

        if abs(rowCount[row]) == size || abs(colCount[col]) == size || abs(diagCount) == size || abs(antiDiagCount) == size {
            return player
        }

        return 0
    }
}

chenbo

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