LEETCODE ALGORITHM:1275. Find Winner on a Tic Tac Toe Game

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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:

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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:

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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:

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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:

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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.

题解

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//枚举所有可能，三行三列及两个对角线
class Solution {
public:
    string tictactoe(vector<vector<int>>& moves) {
        int m[3][3]={0};
        for(int i=0;i<moves.size();i++)
        {
            m[moves[i][0]][moves[i][1]]=(i%2==0)?1:-1;
        }
        int s1=m[0][0]+m[1][1]+m[2][2];
        int s2=m[0][2]+m[1][1]+m[2][0];
        if(s1==3||s2==3) return "A";
        if(s2==-3||s1==-3) return "B";
        for(int i=0;i<3;i++)
        {
            int s=m[i][0]+m[i][1]+m[i][2];
            if(s==3) return "A";
            if(s==-3) return "B";
            s=m[0][i]+m[1][i]+m[2][i];
            if(s==3) return "A";
            if(s==-3) return "B";
        }
        return moves.size()==9?"Draw":"Pending";
        
    }
};