Back to For Beginners

more tic tac toe

For Beginners

Started by phil67rpg October 11, 2012 09:55 PM

30 comments, last by alvaro 11 years, 5 months ago

Bacterius

13,181

October 21, 2012 10:04 PM

is there anyway I can generate a random number only once and do not have it repeat.

If you mean produce a sequence of numbers where no number is repeated, like 3, 1, 9, 5, 2, 4, ... then sure, it's very easy:

1. generate an array [0, 1, 2, 3, 4, ... as much as you need, pretty much put the numbers you want in there]
2. for each element A in the array...
----> select a random element B in the array
----> swap elements A and B
3. iterate through the modified array to get your repeat-free random numbers

See Fisher-Yates shuffle. Is this what you meant?

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”

phil67rpg

458

Author

October 21, 2012 10:07 PM

yes thanks

Bacterius

13,181

October 21, 2012 10:09 PM

Note the algorithm I posted is the naive, inefficient one. The correct one is given on Wikipedia and is much faster:

[source lang="plain"]To shuffle an array a of n elements (indices 0..n-1):
for i from n ? 1 downto 1 do
j ? random integer with 0 ? j ? i
exchange a[j] and a[/source]

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”

dAND3h

220

October 21, 2012 10:18 PM

Also, 0 is counted as a space so in an 8 space array there is in fact 9 spaces.

How can there be 9 spaces in an array of size 8? That makes no sense.

Arkane7 was correct. You will need to change that 8 to a 9. Otherwise, you can change the < sign to <= .

phil67rpg

458

Author

October 21, 2012 10:19 PM

well i have found an algorithm that might work



#include <iostream>

#include <ctime>

using namespace std;

bool isContained(int arr[],int n,int x)

{

for(int i=0;i<n;i++)

{

  if(arr==x)

   return true;

}

return false;

}

int main()

{

srand(time(0));

const int x = 100;

int r[x];

for(int i=0;i<x;i++)

{

  r=1+rand()%x;

  while(isContained(r,i,r))

  {

   r=1+rand()%x;

  }

}

for(int i=0;i<x;i++)

  cout<<r<<"\n";

cout<<"\n\n";

return 0;

}

Bacterius

13,181

October 21, 2012 10:31 PM

That is slow. I gave a link to the proper algorithm in my last post - why not use it? Since you want code:

[source lang="cpp"]#include < iostream>
#include < cstdlib>
#include < ctime>

using namespace std;

void fisherYates(int array[], int length)
{
/* Go over each element backwards. */
for (int t = length - 1; t != 0; t--)
{
/* Select random element in [0..t] */
int r = rand() % (t + 1);

/* Swap them. */
int tmp = array[t];
array[t] = array[r];
array[r] = tmp;
}
}

int main()
{
/* Randomize. */
srand(time(0));

/* Prepare array of N elements. */
const int length = 20;
int array[length];

/* Initialize it. */
for (int t = 0; t < length; ++t) array[t] = t;

/* Shuffle. */
fisherYates(array, length);

/* Print out array. */
for (int t = 0; t < length; ++t) cout < < array[t] < < " ";
cout < < endl;
}[/source]

(remove spaces between << as the source tags munch'em apparently)

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”

phil67rpg

458

Author

October 21, 2012 10:58 PM

cool thanks

phil67rpg

458

Author

October 22, 2012 12:43 AM

[sub]

I have tried fisherYates shuffle but it still does not work.here is my code[/sub]

[sub]

void Computer::move_player_O()
{
srand(time(NULL)); [/sub]
[sub]

const int length=10;
int array[length];
for(int t=1;t<=9;t++)
array[t]=t;
fisherYates(array,length);
player_O=array[t];
t++;
}[/sub]
[sub]

[/sub]
[sub]

void Computer::check_player_O()
{
board[player_O]='O';
}[/sub]

Bacterius

13,181

October 22, 2012 12:57 AM

Why are you incrementing t again inside the loop... the t++ inside the for construct already takes care of that

“If I understand the standard right it is legal and safe to do this but the resulting value could be anything.”

phil67rpg

458

Author

October 22, 2012 01:08 AM

ok i took the t++ out but it still does not work,I am so close to fihishing,any more help would be great.

more tic tac toe

I have tried fisherYates shuffle but it still does not work.here is my code[/sub]

[sub]

void Computer::move_player_O()
{
srand(time(NULL)); [/sub]
[sub]

const int length=10;
int array[length];
for(int t=1;t<=9;t++)
array[t]=t;
fisherYates(array,length);
player_O=array[t];
t++;
}[/sub]
[sub]

[/sub]
[sub]

void Computer::check_player_O()
{
board[player_O]='O';
}[/sub]

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

more tic tac toe

I have tried fisherYates shuffle but it still does not work.here is my code[/sub] [sub]

void Computer::move_player_O() { srand(time(NULL)); [/sub] [sub]

const int length=10; int array[length]; for(int t=1;t<=9;t++) array[t]=t; fisherYates(array,length); player_O=array[t]; t++; }[/sub] [sub]

[/sub] [sub]

void Computer::check_player_O() { board[player_O]='O'; }[/sub]

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines

I have tried fisherYates shuffle but it still does not work.here is my code[/sub]

[sub]

void Computer::move_player_O()
{
srand(time(NULL)); [/sub]
[sub]

const int length=10;
int array[length];
for(int t=1;t<=9;t++)
array[t]=t;
fisherYates(array,length);
player_O=array[t];
t++;
}[/sub]
[sub]

[/sub]
[sub]

void Computer::check_player_O()
{
board[player_O]='O';
}[/sub]