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# a math game for some kids

Posted on 2004-04-15
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I am trying to write a math program for some kids I work with who are visually impaired and just need a little advice on a couple issues.  For one, I'm writing the program in C, and I'm trying to generate random numbers for the problems which are asked.  I seeded the generator with srand((unsigned)time(NULL)) at the beginning and am trying to exclude 0 from being generated as a possible number for a problem.  For example: firstint = rand()%maxint.  Maxint is defined according to how far the player has progressed in the game.  I want the generated number to be between 1 and maxint.  Any suggestions?  Thanks a lot in advance.
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Question by:guyster104
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LVL 84

Accepted Solution

ozo earned 50 total points
ID: 10834614
firstint = 1+rand()%maxint;
0

LVL 11

Expert Comment

ID: 10835054
if you use ozo way you could end up one over MaxInt so you could use

FirstInt = 1 + rand() % (MaxInt-1);
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LVL 84

Expert Comment

ID: 10838008
1 + rand() % (MaxInt-1); will never return a value of MaxInt
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LVL 11

Expert Comment

ID: 10841226
why wouldnt it?

Say MaxInt = 5

I have took one away from MaxInt so,

the line of code could look like

rand() % 4

That means a number between 0 and 4 could be generated. The I have added one to the result so a number between 1 and 5 can be generated.

If your talking about the order of precedance guyster should use:

FirstInt = (rand() % (MaxInt-1)) + 1
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LVL 1

Expert Comment

ID: 10846887
Its been a few years since I have used C, so the loop construct is probably wrong, but the concept is there.

If you are not too sure about what Max & Min values you may end up with, you could always build in a safety net.

do
FirstInt = 1 + rand() % (MaxInt-1);
until Firstint >=1 and FirstInt <=MaxInt
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Author Comment

ID: 10862540
Ozo's method worked well.  The program is well on its way to completion.  I would love to spice it up with some visual elements, such as dialogue boxes and a Windows style interface, but since I myself am visually impaired, don't know if I want to brave that one just yet.  Thanks to all for the suggestions.  Keep up the good work.

Guy
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