aleshik1
join:2004-07-10
Newark, NJ
 ·Optimum Online
1 edit | please tell me why my c++ app doesnt work?
#include
using namespace std;
int main(){
int number;
int factor;
int remainder;
int test;
for (number=4;;number++)
{
for (factor=2;factornumber;factor++)
{
int remainder=number/factor;
if (int remainder=0){int test=0;}
for(;test=0;number++){}
}
if(test!=0){cout number;}
}
return 0;
}
I want it to display prime numbers from 4 and above.By tweaking it I can either get it to display all numbers or none at all.I cant seem to get it right.  |
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PToN
join:2001-10-04
Houston, TX
| your for loops are all wrong. Check your book and re-read the looping chapter. Or make a google search so you can understand it.
It should look something like:
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Steve
I'm a PC, so shut up
Consultant
join:2001-03-10
Yorba Linda, CA | reply to aleshik1
You'll also need to use the [code]
tags so we can see your code; many of us (including me) won't really even look at stuff that's essentially unformatted. |
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cowboyro
join:2000-10-11
Shelton, CT | reply to PToN
condition doens't always have to exist in his case since it's for all numbers - so basically an infinite loop  |
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cowboyro
join:2000-10-11
Shelton, CT
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| reply to aleshik1
this shoud give a hint - haven't checked it though
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cowboyro
join:2000-10-11
Shelton, CT
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| reply to aleshik1
Anyway this is the low level, brute force approach...
However it can be refined since:
-all even numbers greater than 2 are NOT prime as they can be divided by 2, so only odd numbers should be tested
-divisors that are even numbers should not be tested as they are multiple of 2, and you know the odd numbers that you are testing cannot be divided by 2 with a reminder of 0 
Therefore you can tweak the code to start with number 3 for testing and increment by 2, and for divisor start with number 3 and increment by 2. |
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PToN
join:2001-10-04
Houston, TX
| reply to cowboyro
quote:
from 4 and above
I missed the "above" part :) , even then he could still used a condition
But i see what you saying :p |
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