Nim Game Human vs Computer

#include <iostream>
#include <string>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>


using namespace std;


#define inf (1<<30)-1
#define SIZE 10001
#define forn(i,n) for (i=0;i<n;i++)
#define forr(i,n) for (i=n-1;i>=0;i--)
#define forab(i,p,k) for (i=p; i<=k;i++)




string players[3] = { "HUMAN", "COMPUTER" };


int gameBoard[100001],n;
int Score,currentPlayer,Round;


void printGameBoard(int gameBoard[])
{
    int i;
    printf("\nGame State: ");
   forn(i,n) printf("\t%d",gameBoard[i]);
}


int maxIndex(int arr[])
{
    int index = 0,i;
    int Max = arr[0];
    forn(i,n)
    if(Max < arr[i])
    {
        Max = arr[i];
        index = i;
    }
    return index;
}




void humanPlays(int gameBoard[])
{
    int Stack,Piles;


    invalid :


    printf("\nFrom Which Stack ... : ");
    scanf("%d",&Stack);


    printf("\nNumber of Piles to remove : ");
    scanf("%d",&Piles);


    if(gameBoard[Stack - 1] == 0)
    {
        printf("\nInvalid move !!!!");
        goto invalid;
    }
    else if(Piles > gameBoard[Stack - 1]) goto invalid;
    else gameBoard[Stack - 1] -= Piles;
}




void computerPlays(int game[],int n)
{
    int Stack, len = n, XOR = 0,i,afterandGame[n+1];


    forn(i,len) XOR ^= game[i];


    if (XOR == 0)
    {
         // min move to make game last longer and push user to mistake
        while(gameBoard[Stack = (int)(rand() % len)] == 0);
        gameBoard[Stack]--;
    }
    else
    {
        forn(i,len) afterandGame[i] = gameBoard[i] & XOR;
        Stack = maxIndex(afterandGame);
        gameBoard[Stack] -= (gameBoard[Stack] - (XOR ^ gameBoard[Stack]));
    }
}




int main()
{
    int i;
    while(true)
    {
        Score = -1;


        currentPlayer = Round = 0;
        printf("Start Nim Game : \n\nPlease Enter the no of Stack : ");
        scanf("%d",&n);


        forn(i,n) gameBoard[i] = rand() % 20 + 1;


        while(Score != 0)
        {
            printGameBoard(gameBoard);
            currentPlayer = Round % 2;


            cout << endl << endl;
            cout << players[currentPlayer] << " Plays. " << endl;
            cout << endl << endl;


if (currentPlayer == 0) humanPlays(gameBoard);
else computerPlays(gameBoard,n);


Score = 0;
forn(i,n) Score += gameBoard[i];
Round++;
        }
        cout << players[currentPlayer] << "  wins.\n" << endl;
    }
    return 0;
}