1275. Find Winner on a Tic Tac Toe Game

1275. Find Winner on a Tic Tac Toe Game #

题目 #

Tic-tac-toe is played by two players A and B on a 3 x 3 grid.

Here are the rules of Tic-Tac-Toe:

  • Players take turns placing characters into empty squares (” “).
  • The first player A always places “X” characters, while the second player B always places “O” characters.
  • “X” and “O” characters are always placed into empty squares, never on filled ones.
  • The game ends when there are 3 of the same (non-empty) character filling any row, column, or diagonal.
  • The game also ends if all squares are non-empty.
  • No more moves can be played if the game is over.

Given an array moves where each element is another array of size 2 corresponding to the row and column of the grid where they mark their respective character in the order in which A and B play.

Return the winner of the game if it exists (A or B), in case the game ends in a draw return “Draw”, if there are still movements to play return “Pending”.

You can assume that moves is valid (It follows the rules of Tic-Tac-Toe), the grid is initially empty and A will play first.

Example 1:

Input: moves = [[0,0],[2,0],[1,1],[2,1],[2,2]]
Output: "A"
Explanation: "A" wins, he always plays first.
"X  "    "X  "    "X  "    "X  "    "X  "
"   " -> "   " -> " X " -> " X " -> " X "
"   "    "O  "    "O  "    "OO "    "OOX"

Example 2:

Input: moves = [[0,0],[1,1],[0,1],[0,2],[1,0],[2,0]]
Output: "B"
Explanation: "B" wins.
"X  "    "X  "    "XX "    "XXO"    "XXO"    "XXO"
"   " -> " O " -> " O " -> " O " -> "XO " -> "XO " 
"   "    "   "    "   "    "   "    "   "    "O  "

Example 3:

Input: moves = [[0,0],[1,1],[2,0],[1,0],[1,2],[2,1],[0,1],[0,2],[2,2]]
Output: "Draw"
Explanation: The game ends in a draw since there are no moves to make.
"XXO"
"OOX"
"XOX"

Example 4:

Input: moves = [[0,0],[1,1]]
Output: "Pending"
Explanation: The game has not finished yet.
"X  "
" O "
"   "

Constraints:

  • 1 <= moves.length <= 9
  • moves[i].length == 2
  • 0 <= moves[i][j] <= 2
  • There are no repeated elements on moves.
  • moves follow the rules of tic tac toe.

题目大意 #

A 和 B 在一个 3 x 3 的网格上玩井字棋。井字棋游戏的规则如下:

  • 玩家轮流将棋子放在空方格 (” “) 上。
  • 第一个玩家 A 总是用 “X” 作为棋子,而第二个玩家 B 总是用 “O” 作为棋子。
  • “X” 和 “O” 只能放在空方格中,而不能放在已经被占用的方格上。
  • 只要有 3 个相同的(非空)棋子排成一条直线(行、列、对角线)时,游戏结束。
  • 如果所有方块都放满棋子(不为空),游戏也会结束。
  • 游戏结束后,棋子无法再进行任何移动。

给你一个数组 moves,其中每个元素是大小为 2 的另一个数组(元素分别对应网格的行和列),它按照 A 和 B 的行动顺序(先 A 后 B)记录了两人各自的棋子位置。如果游戏存在获胜者(A 或 B),就返回该游戏的获胜者;如果游戏以平局结束,则返回 “Draw”;如果仍会有行动(游戏未结束),则返回 “Pending”。你可以假设 moves 都 有效(遵循井字棋规则),网格最初是空的,A 将先行动。

提示:

  • 1 <= moves.length <= 9
  • moves[i].length == 2
  • 0 <= moves[i][j] <= 2
  • moves 里没有重复的元素。
  • moves 遵循井字棋的规则。

解题思路 #

  • 两人玩 3*3 井字棋,A 先走,B 再走。谁能获胜就输出谁,如果平局输出 “Draw”,如果游戏还未结束,输出 “Pending”。游戏规则:谁能先占满行、列或者对角线任意一条线,谁就赢。
  • 简单题。题目给定 move 数组最多 3 步,而要赢得比赛,必须走满 3 步,所以可以先模拟,按照给的步数数组把 A 和 B 的步数都放在棋盘上。然后依次判断行、列,对角线的三种情况。如果都判完了,剩下的情况就是平局和死局的情况。

代码 #


package leetcode

func tictactoe(moves [][]int) string {
	board := [3][3]byte{}
	for i := 0; i < len(moves); i++ {
		if i%2 == 0 {
			board[moves[i][0]][moves[i][1]] = 'X'
		} else {
			board[moves[i][0]][moves[i][1]] = 'O'
		}
	}
	for i := 0; i < 3; i++ {
		if board[i][0] == 'X' && board[i][1] == 'X' && board[i][2] == 'X' {
			return "A"
		}
		if board[i][0] == 'O' && board[i][1] == 'O' && board[i][2] == 'O' {
			return "B"
		}
		if board[0][i] == 'X' && board[1][i] == 'X' && board[2][i] == 'X' {
			return "A"
		}
		if board[0][i] == 'O' && board[1][i] == 'O' && board[2][i] == 'O' {
			return "B"
		}
	}
	if board[0][0] == 'X' && board[1][1] == 'X' && board[2][2] == 'X' {
		return "A"
	}
	if board[0][0] == 'O' && board[1][1] == 'O' && board[2][2] == 'O' {
		return "B"
	}
	if board[0][2] == 'X' && board[1][1] == 'X' && board[2][0] == 'X' {
		return "A"
	}
	if board[0][2] == 'O' && board[1][1] == 'O' && board[2][0] == 'O' {
		return "B"
	}
	if len(moves) < 9 {
		return "Pending"
	}
	return "Draw"
}


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