C++Talk.NET

jw · Guest

hi all;
i have a function like this,
it always rands the same number and gives error if i take the srand
function out of the for loop
void list::getWords()
{ int num;

for(int m=0;m<20;m++)
{
srand((unsigned)time( NULL ));
num=(rand()%41)-1;
node *ptr;
ptr=new node;
ptr->word=wordsall[num];
append(ptr);//appends to the linked list
}
}

Stephen M. Webb · Guest

Why reseed the random number generator on each iteration? That's
pretty much guaranteed to give you a nonrandom distribution.

--smw

Kristo · Guest

jw wrote:

jw · Guest

if i take it out of the loop it crashes while running,but now it doesnt
crash but always rands the same number

Rolf Magnus · Guest

jw wrote:

Stephen M. Webb · Guest

num=(rand()%41)-1;
ptr->word=wordsall[num];

Aside from the lack of randomness of your generated numbers (rand()
fails tests for randomness in its little bits), using a negative number
as an array index is probably not what you want.

--smw

jw · Guest

not in a line the program crashes and stops running if i take it out
of the loop

Howard · Guest

"jw" <jackwht (AT) gmail (DOT) com> wrote

jw · Guest

yeah i think the problem is there it gives a negative number but it
must not give a negative number because if we take the mod of a number
it doesnt give 0

W Marsh · Guest

On 28 Nov 2005 09:28:41 -0800, "jw" <jackwht (AT) gmail (DOT) com> wrote:

Howard · Guest

"jw" <jackwht (AT) gmail (DOT) com> wrote

jw · Guest

here is the whole code;
#include<iostream>
#include<fstream>
#include<vector>
#include<string>
#include<ctime>
using namespace std;
#ifndef NULL
#define NULL (short) 0
#endif

char
*words[40]={"come","go","school","nice","united","college","apple","orange","old","days","who","knows"};

//*******************node clasim*******************
class node{
private:
string word;
node *next;
public:

node()
{
next=NULL;
}

friend class list;

void display()
{
cout< }
};

//*****************list clasim*********************
class list{
private:
node *head,*tail,*TOP;
void append(node *new_node);

public:
list()
{
TOP=new node;
head=tail=TOP;
TOP->next=NULL;
}
//~list()delete...
void getWords();
void displayAll();

};

void list::displayAll()
{

node *py;

py=head;

if(py==NULL)
{
cout<<"nothing to show"< }
while(py!=NULL){//while py points sth reasonable

py->display();
py=py->next;
}

}

void list::append(node *ptr){

if(TOP->next==NULL)//first element
{ TOP->next=ptr;
head=ptr;
tail=ptr;
}
else
{

tail->next=ptr;
tail=ptr;

}

}

void list::getWords()
{ int num;
srand((unsigned)time( NULL ));
for(int m=0;m<20;m++)
{

num=(rand()%41);

node *ptr;
ptr=new node;
ptr->word=words[num];
append(ptr);
}
}

void main()
{
list thelist;
thelist.getWords();
thelist.displayAll();
}

Howard · Guest

"jw" <jackwht (AT) gmail (DOT) com> wrote

jw · Guest

thanks,am so sorry for such a silly mistake forgive me all

Default User · Guest

Howard wrote: