Mark alternating moves on a three-by-three board, test all rows, columns, and diagonals, then distinguish draw from pending by move count.
Complexity
O(m) time for the moves and O(1) space.
09 Sept 2026•Easy•Go / Python / TypeScript
Find Winner on a Tic Tac Toe Game
Determine the winner or current state after a valid sequence of tic-tac-toe moves.
Solution files
Go•find-winner-on-a-tic-tac-toe-game/solution.go
package main
func tictactoe(moves [][]int) string {
board := [3][3]int{}
for index, move := range moves {
if index%2 == 0 {
board[move[0]][move[1]] = 1
} else {
board[move[0]][move[1]] = -1
}
}
for index := 0; index < 3; index++ {
row, column := 0, 0
for offset := 0; offset < 3; offset++ {
row += board[index][offset]
column += board[offset][index]
}
if row == 3 || column == 3 {
return "A"
}
if row == -3 || column == -3 {
return "B"
}
}
first, second := board[0][0]+board[1][1]+board[2][2], board[0][2]+board[1][1]+board[2][0]
if first == 3 || second == 3 {
return "A"
}
if first == -3 || second == -3 {
return "B"
}
if len(moves) == 9 {
return "Draw"
}
return "Pending"
}
Python•find-winner-on-a-tic-tac-toe-game/solution.py
class Solution:
def tictactoe(self, moves: list[list[int]]) -> str:
board = [[0] * 3 for _ in range(3)]
for index, (row, column) in enumerate(moves): board[row][column] = 1 if index % 2 == 0 else -1
lines = board + [list(column) for column in zip(*board)] + [[board[i][i] for i in range(3)], [board[i][2 - i] for i in range(3)]]
for line in lines:
if sum(line) == 3: return "A"
if sum(line) == -3: return "B"
return "Draw" if len(moves) == 9 else "Pending"
TypeScript•find-winner-on-a-tic-tac-toe-game/solution.ts
function tictactoe(moves: number[][]): string {
const board = Array.from({ length: 3 }, () => new Array<number>(3).fill(0)); moves.forEach(([row, column], index) => { board[row][column] = index % 2 === 0 ? 1 : -1; });
const lines = [...board, ...[0, 1, 2].map((column) => board.map((row) => row[column])), [board[0][0], board[1][1], board[2][2]], [board[0][2], board[1][1], board[2][0]]];
for (const line of lines) { const sum = line.reduce((total, value) => total + value, 0); if (sum === 3) return "A"; if (sum === -3) return "B"; }
return moves.length === 9 ? "Draw" : "Pending";
}