DSPS Practical : Tic Tac Toe

#include <iostream>
using namespace std;
char sq[10] = {'0','1','2','3','4','5','6','7','8','9'};
int checkwin();
void board();

int main()
{
   int player=1,i,ch;
   char mark;
   do{
      board();
      player=(player%2)?1:2;
      cout<<"Player"<<player<<"Enter Number"<<endl;
      cin>>ch;
      mark=(player==1)?'x':'0';

    if(ch==1&& sq[1]=='1')
            sq [1]=mark;

        else if(ch==2 && sq[2]=='2')
            sq [2]=mark;

        else if(ch==3 && sq[3]=='3')
            sq [3]=mark;

        else if(ch==4 && sq[4]=='4')
            sq[4]=mark;

        else if(ch==5 && sq[5]=='5')
            sq[5]=mark;

        else if(ch==6 && sq[6]=='6')
            sq[6]=mark;

        else if(ch==7 && sq[7]=='7')
            sq[7]=mark;

        else if(ch==8 && sq[8]=='8')
            sq[8]=mark;

        else if(ch==9 && sq[9]=='9')
            sq[9]=mark;
        else{
            cout<<"Please try again"<<endl;
            player--;
        }
        i=checkwin();
        player++;
      }while(i==-1);
          board();
       if(i==1)
        cout<<"Player "<<--player<<" wins ";
       else
           cout<<"Game draw";
  return 0;

}

int checkwin()
{
         if (sq[1]==sq[2] && sq[2]==sq[3])
        return 1;

    else if (sq[4]==sq[5] && sq[5]==sq[6])
        return 1;

    else if (sq[7]==sq[8] && sq[8]==sq[9])
        return 1;

    else if (sq[1]==sq[4] && sq[4]==sq[7])
        return 1;

    else if (sq[2]==sq[5] && sq[5]==sq[8])
        return 1;

    else if (sq[3]==sq[6] && sq[6]==sq[9])
        return 1;

    else if (sq[1]==sq[5] && sq[5]==sq[9])
        return 1;

    else if (sq[3]==sq[5] && sq[5]==sq[7])
        return 1;
//if nothing then==
    else if (sq[1]!='1'&& sq[2]!='2'&& sq[3]!='3' &&
             sq[4]!='4'&& sq[5]!='5'&& sq[6]!= '6'
             && sq[7] != '7' && sq[8] != '8' && sq[9] != '9')
        return 0;
    else
        return -1;
}

void board(){
    cout<<"Hello! This is Tic Tac Toe!"<<endl;
    cout << "  " << sq[1] << "  |  " << sq[2] << "  |  " << sq[3] << endl;
    cout << "_____|_____|_____" << endl;
    cout << "     |     |     " << endl;
    cout << "  " << sq[4] << "  |  " << sq[5] << "  |  " << sq[6] << endl;
    cout << "_____|_____|_____" << endl;
    cout << "     |     |     " << endl;
    cout << "  " << sq[7] << "  |  " << sq[8] << "  |  " << sq[9] << endl;

}

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