A Tic-Tac-Toe board is given as a string array board
. Return True if and
only if it is possible to reach this board position during the course of a
valid tic-tac-toe game.
The board
is a 3 x 3 array, and consists of characters " "
, "X"
, and
"O"
. The " " character represents an empty square.
Here are the rules of Tic-Tac-Toe:
Players take turns placing characters into empty squares (" ").
The first player always places "X" characters, while the second player always places "O" characters.
"X" and "O" characters are always placed into empty squares, never 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.
Example 1: Input: board = ["O ", " ", " "] Output: false Explanation: The first player always plays "X".
Example 2: Input: board = ["XOX", " X ", " "] Output: false Explanation: Players take turns making moves.
Example 3: Input: board = ["XXX", " ", "OOO"] Output: false
Example 4: Input: board = ["XOX", "O O", "XOX"] Output: true
Note:
board
is a length-3 array of strings, where each string board[i]
has length 3.board[i][j]
is a character in the set {" ", "X", "O"}
.# @lc code=start
using LeetCode
function validTicTacToe(board::Array{Char})::Bool
n_X, n_O = 0, 0
for x in board
if x == 'X'
n_X += 1
elseif x == 'O'
n_O += 1
end
end
if n_O > n_X || n_X >= n_O + 2
false
elseif n_X >= 3
if n_X == n_O
if is_win(board, 'X')
false ## Impossible! n_X should == x_O + 1
else
true
end
else
# @assert n_X == n_O + 1
if is_win(board, 'O')
false ## Impossible!
else
true
end
end
else
true
end
end
function is_win(b, x)
return b[1] == b[2] == b[3] == x ||
b[4] == b[5] == b[6] == x ||
b[7] == b[8] == b[9] == x ||
b[1] == b[4] == b[7] == x ||
b[2] == b[5] == b[8] == x ||
b[3] == b[6] == b[9] == x ||
b[1] == b[5] == b[9] == x ||
b[3] == b[5] == b[7] == x
end
# @lc code=end
is_win (generic function with 1 method)
This notebook was generated using Literate.jl.