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LeetCode 348, Medium. Topics: Design, Array, Hash Table, Matrix, Simulation. View on LeetCode. Generate this problem as a practice environment: tested reference solution, 15 parametrized pytest cases, and a playground notebook:

Problem

Assume the following rules are for the tic-tac-toe game on an n x n board between two players:
  1. A move is guaranteed to be valid and is placed on an empty block.
  2. Once a winning condition is reached, no more moves are allowed.
  3. A player who succeeds in placing n of their marks in a horizontal, vertical, or diagonal row wins the game.
Implement the TicTacToe class:
  • TicTacToe(int n) Initializes the object the size of the board n.
  • int move(int row, int col, int player) Indicates that the player with id player plays at the cell (row, col) of the board. The move is guaranteed to be a valid move, and the two players alternate in making moves. Return
    • 0 if there is no winner after the move,
    • 1 if player 1 is the winner after the move, or
    • 2 if player 2 is the winner after the move.

Examples

Constraints

  • 2 <= n <= 100
  • player is 1 or 2.
  • 0 <= row, col < n
  • (row, col) are unique for each different call to move.
  • At most n^2 calls will be made to move.
Follow-up: Could you do better than O(n^2) per move() operation?

Solution

Reference implementation from solution.py on GitHub, full suite in test_solution.py:

Complexity

Tags

NeetCode All.
Last modified on September 7, 2026