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Views: 2361 | Replies: 14
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Join Date: Apr 2005
Posts: 30
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HAving trouble with my pointer arithmetic, any ideas appreciated
My orgional code
converted but wrong
my struct
if you want the whole code let me know
My orgional code
Activity p[51];
for ( int i = 1; i <= n; ++i ) {
// Read the activity records.
pert >> p[i].i >> p[i].j >> p[i].pt
>> p[i].prt >> p[i].ot;
pert.getline(p[i].desc,21);Activity **p = new Activity*[51];
for ( i = 1; i <= n; ++i ) {
if (p[i].i == NULL)
break;
pert >> (*p+i)->i >> *(p+i)->j >> *(p+i)->pt
>> *(p+i)->prt >> *(p+i)->ot;
pert.getline(*(p+i)->desc,21);
}my struct
struct Activity {
int i, // Beginning node number.
j; // Ending node number.
float pt, // Pessimistic time.
prt, // Most probable time.
ot; // Optimistic time.
char desc[21]; // Activity description.
};if you want the whole code let me know
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Join Date: Feb 2005
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Posting Pro in Training
Why are you starting your array at 1 instead of 0? Also, how big is n?
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Join Date: Apr 2005
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started the array at 1 becaused that was a requirement of the assigmnent. n is the number of activities and in the test case its 11. I'm not sure i can dynamically allocate for n without alot of copying.
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Join Date: Feb 2005
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Can you indicate what the 'problem' is? Is it when you attempt to print the contents of the array?
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Join Date: Apr 2005
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Originally Posted by winbatch
Can you indicate what the 'problem' is? Is it when you attempt to print the contents of the array?
I am trying to read each line as a new activity and then have all the activities in an array.
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Join Date: Feb 2005
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Posting Pro in Training
Post the code where you are trying to utilize/print out the array to show where the problem manifests itself..
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Join Date: May 2005
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Posting Whiz in Training
Was this what you were trying to do?
Activity **p = new Activity*[51];
for ( int i = 1; i <= n; ++i ) {
// Read the activity records.
pert >> (*(p+i))->i >> (*(p+i))->j >> (*(p+i))->pt
>> (*(p+i))->prt >> (*(p+i))->ot;
pert.getline((*(p+i))->desc,21);
} •
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Join Date: Apr 2005
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Originally Posted by Dogtree
Was this what you were trying to do?
Activity **p = new Activity*[51]; for ( int i = 1; i <= n; ++i ) { // Read the activity records. pert >> (*(p+i))->i >> (*(p+i))->j >> (*(p+i))->pt >> (*(p+i))->prt >> (*(p+i))->ot; pert.getline((*(p+i))->desc,21); }
This is how i implemented it
for ( i = 1; i <= n; ++i ) {
cout<< "test5" << endl;
if ((*(p+i))->i == NULL){
cout<< "test4" << endl;
break;
}
cout<< "test4" << endl;
// Read the activity records.
pert >> (*(p+i))->i >> (*(p+i))->j >> (*(p+i))->pt
>> (*(p+i))->prt >> (*(p+i))->ot;
pert.getline((*(p+i))->desc,21);
cout << (*(p+i))->i << endl;
} •
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Join Date: May 2005
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Posting Whiz in Training
Either n is bigger than 50, which is the last accessible index in your array, or you aren't allocating memory to each Activity pointer in the array. You probably want to allocate the initial memory like this:
Then you release the memory like this:
Unless you do this, you'll have to initialize each pointer to an existing object before you try to dereference it.
Activity **p = new Activity*[51]; for (int i = 0; i < 51; i++) p[i] = new Activity;
for (int i = 0; i < 51; i++) delete [] p[i]; delete p;
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Join Date: Apr 2005
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ok i adjusted some things as that doesnt seem to be what i wanted, but my code still wont read in the text file and then allow me to print it out as needed.
the first line of the text file reads
1 2 1 2 4 ORD.FIXTURES
but when i do
cout << (p+i)->i << endl;
i get a 0
and the final out put is just garbage ( if you want the final out put code i can post it but its large)
Activity *p = new Activity [51];
for (i = 1; i <= n; ++i )
{
cout<< "test5" << endl;
if ((p+i)->i == NULL)
{
cout<< "test6" << endl;
break;
}
cout<< "test7" << endl;
// Read the activity records.
pert >> (p+i)->i >> (p+i)->j >> (p+i)->pt
>> (p+i)->prt >> (p+i)->ot;
pert.getline((p+i)->desc,21);
cout << (p+i)->i << endl;
}1 2 1 2 4 ORD.FIXTURES
but when i do
cout << (p+i)->i << endl;
i get a 0
and the final out put is just garbage ( if you want the final out put code i can post it but its large)
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