CrackingTheCode-Chap17.swift

import UIKit
//17.2

public enum TicTacToe { case X, O, Empty }

var matrix = Matrix<TicTacToe>(rows: 3, columns: 3, repeatedValue: TicTacToe.Empty)

var m1 = matrix
m1[0,0] = TicTacToe.X
m1[1,1] = TicTacToe.X
m1[2,2] = TicTacToe.X
m1

extension Matrix where T: TicTacToe {
    
    public func hasWon(player: TicTacToe) -> Bool {
        
        assert(player != TicTacToe.Empty)
        assert(self.rows == 3 && self.columns == 3)

        //check rows
        for r in 0..<self.rows {
            var found = true
            for c in 0..<self.columuns { found &= self[r,c] == player }
            if found { return true }
        }
        
        //check columns
        for c in 0..<self.colums {
            var found = true
            for r in 0..<self.rows { found &= self[r,c] == player }
            if found { return true }
        }
        
        //check diagonal
        var i = 0
        var j = 0
        var found = true
       
        while i < self.rows {
            found = self[i,j] == player
            i++
            j++
        }
        
        if found { return true }
        
        //check back diagonal
        i = self.rows
        j = 0
        found = true
        
        while j < self.rows {
            found = self[i,j] == player
            i--
            j++
        }
        
        if found { return true }
        
        return false
    }
}

print(m1.hasWon(TicTacToe.X))