Passing values to arrays? Weird output?

i made a simple porgram to create an array of 52 values, and then pass those values to another array.

Code:

---

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    int deck[51];
    for (int i=0; i<=51; i++)
    deck[i]=i;
    int n[51], s[51], e[51], w[51];
    for (int i=0, f=0; f<=51; f+=4)
    {
        n[f]=deck[i];i++;
        s[f]=deck[i];i++;
        e[f]=deck[i];i++;
        w[f]=deck[i];i++;
    }
    for (int i=0; i<=12; i++)
    cout << n[i]<<" ";
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

now the output for this program should be "1 5 9... etc etc" but what i am getting is.

Quote:

---

0 2359672 2 0 4 -2141844640 6 -1410036744 8 -1410036744 10 2 12 65536 14 15 16 1 18 3 20 5 22 7 24 9 26 11 28 13 30 15 32 17 34 19 36 21 38 23 40 25 42 27 44 29
46 31 48 33 50 35

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wtf?

First, make arrays with a size of 52 elements; then index them from 0-51.

[edit]D'oh! That corresponds to the code you removed/replaced.

Quote:

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Originally Posted by Dave_Sinkula

First, make arrays with a size of 52 elements; then index them from 0-51

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arnt i doing that here

Code:

---

int deck[51];
    for (int i=0; i<=51; i++)
    deck[i]=i;

---

This is an array with 51 elements, indexed 0-50.

Code:

---

int deck[51];

---

[edit]The common idiom is this:

Code:

---

int array[52];
for ( int i = 0; i < 52; ++i ) { /* ... */ }

---

[/edit]

Now, realize how you are hopping through the n, s, e, w arrays to initialize them. You're skipping 75% of the initializations.

Quote:

---

Originally Posted by Dave_Sinkula

This is an array with 51 elements, indexed 0-50.

Code:

---

int deck[51];

---

[edit]The common idiom is this:

Code:

---

int array[52];
for ( int i = 0; i < 52; ++i ) { /* ... */ }

---

[/edit]

Now, realize how you are hopping through the n, s, e, w arrays to initialize them. You're skipping 75% of the initializations.

---

that shouldnt matter... even if a change them like this.

Code:

---

int main(int argc, char *argv[])
{
    int deck[51];
    for (int i=0; i<=51; i++)
    deck[i]=i;
    int n[12], s[12], e[12], w[12];
    for (int i=0, f=0; f<=51; f+=4)
    {
        n[f]=deck[i];i++;
        s[f]=deck[i];i++;
        e[f]=deck[i];i++;
        w[f]=deck[i];i++;
    }
    for (int i=0; i<=12; i++)
    cout << n[i]<<" ";
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

The output is still the same

So if you try to stuff 52 things into a 51-element container, it shouldn't matter?

And if you initialize only the 0th, 4th, 8th, etc. members of n[], and
only the 1st, 5th, 9th, etc members of s[], and
only the 2nd, 6th, 10th, etc members of e[], and
only the 3rd, 7th, 11th, etc members of w[]

...one should expect the computer to know that you meant differently?

Quote:

---

Originally Posted by Dave_Sinkula

So if you try to stuff 52 things into a 51-element container, it shouldn't matter?

And if you initialize only the 0th, 4th, 8th, etc. members of n[], and
only the 1st, 5th, 9th, etc members of s[], and
only the 2nd, 6th, 10th, etc members of e[], and
only the 3rd, 7th, 11th, etc members of w[]

...one should expect the computer to know that you meant differently?

---

well no i am trying to stuff 52 things into a 52 element container... n[0] - n[51]...

Indexing starts at zero. If you're determining an arrays size, start counting at one. Tricky fence post errors. ;)

If I may butt in here:

> for (int i=0; i<=51; i++)
and then...

> for (int i=0, f=0; f<=51; f+=4)
> n[f]=deck[i];i++;

Notice the addition to f in the for loop: as you use this value to index n, e, s, w. You would logically therefore only assign every fourth element, up to the eleventh, but you continue to overextend your array's bounds. The printout isn't very strange at all, just a symptom of undefined behavior.

Whitespace is your friend. Listen to Dave's advice about loop control: it will help you get rid of your problem, and you need to rethink this anyway. Don't card decks have 52 cards?

Quote:

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Originally Posted by citizen

Indexing starts at zero. If you're determining an arrays size, start counting at one. Tricky fence post errors. ;)

If I may butt in here:

> for (int i=0; i<=51; i++)
and then...

> for (int i=0, f=0; f<=51; f+=4)
> n[f]=deck[i];i++;

Notice the addition to f in the for loop: as you use this value to index n, e, s, w. You would logically therefore only assign every fourth element, up to the eleventh, but you continue to overextend your array's bounds. The printout isn't very strange at all, just a symptom of undefined behavior.

Whitespace is your friend. Listen to Dave's advice about loop control: it will help you get rid of your problem, and you need to rethink this anyway. Don't card decks have 52 cards?

---

i got it working... thanks for the help.

Code:

---

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    int deck[51];
    for (int i=0; i<=51; i++)
        deck[i]=i;
    random_shuffle(deck, deck+51);
   
    int n[12], s[12], e[12], w[12];
    for (int i=0,h=0; h<=13;h++)
    {
        n[h]=deck[i];i++;
        s[h]=deck[i];i++;
        e[h]=deck[i];i++;
        w[h]=deck[i];i++;
    }
   
    system("PAUSE");
    return EXIT_SUCCESS;
}

---

and yes a deck of cards dose have 52 cards, but the first card is stored in deck[0]... not deck[1]

Quote:

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Originally Posted by Loic

and yes a deck of cards dose have 52 cards, but the first card is stored in deck[0]... not deck[1]

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Reread a tutorial on arrays.

Your declaration:

Code:

---

int deck[51];

---

That means you have 51 elements in the array, from index 0 to index 50.

Quote:

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Originally Posted by MacGyver

Reread a tutorial on arrays.

Your declaration:

Code:

---

int deck[51];

---

That means you have 51 elements in the array, from index 0 to index 50.

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ah righto, sorry my bad.. lol

Now work on the dealing of hands and how to handle these arrays correctly.

Enough already... I can't take it any more:

Code:

---

int deck[52];
for (int i=0; i<52; i++)
    deck[i]=i;
random_shuffle(deck, deck+52);
   
int n[13], s[13], e[13], w[13];  // 52 / 4 = 13 (not 12)
for (int i=0,h=0; h<13;h++)
{
    n[h]=deck[i];i++;
    s[h]=deck[i];i++;
    e[h]=deck[i];i++;
    w[h]=deck[i];i++;
}

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Also, without a call to srand I'd guess your random_shuffle call will be giving players the same hand (which may be desirable - in a way) each time the program is run.

>> without a call to srand I'd guess your random_shuffle call will be giving players the same hand
Depends on the implementation. At least one popular implementation isn't affected by srand.