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| Finding Prime numbers with C | ||
| Author btcdtc Views 17 Posted at 2008/8/27 05:28 [View In Forum] | ||
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Hi,wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq I have another assignment, for my C programming class im having difficulty with.wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq The program is suppose to find the Nth prime number, im suppose to use pointers and functions, but im trying to just get it to work without any of that yet. Below is what I have come up with, I thought it would work, but it doesnt. Once I enter in a number, is doesnt do anything.wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq Can anyone help?wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq #include <stdio.h>wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq int main(void)wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq {wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq int choice;wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq int count=2;wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq printf("PRIME NUMBER CALCULATOR\n");wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq printf("\nChoose a Prime number=>");wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq scanf_s("%d",&choice);wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq while(1){wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq if(choice==1 || choice==2)wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq {printf("The Number is %d",choice);wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq break;}wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq else if(count%2==0 || count%3==0 || count%5==0 || count%7==0 || count==0)wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq continue;wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq elsewtsvxiwzhq wtsvxiwzhq wtsvxiwzhq count =2;wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq if(count==choice)wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq break;wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq }wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq printf("The number is %d",count);wtsvxiwzhq wtsvxiwzhq Hi,wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq What you need to do is have a look in your help files on what the 'continue' statement does. Understanding this will let you know why the program is not doing what you want it to.wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq Try putting some break points in at the if and else statements in your while loop and watch what happens!wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq Cheers,wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq Nick wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq wtsvxiwzhq Added after 8 minutes: |
| Reply No. | Replier | Total Replies 9 [View All Replies] [New Reply] | Replied at |
| 1 | lassa | Hmm I read up on the continue statement, but im still kind of confused. If the remainder is equal to zero that means its not prime, so I thought my continue would just bypass the rest of the loop, and jump back up to the beginning? | 2008/8/27 05:28 |
| 2 | dongyea | That's what the continue statement does, it is always returning to the start of the loop as the count is increasing. Your count starts at 2 and avery loop you add 2 to it so the remainder of your modulus divide is always going to be 0! edit,: infact, you are jumping to the start o fthe loop before you increment your count, so the count variable remains at 2. |
2008/8/27 05:28 |
| 3 | hgping | Ahh I see what you mean. Im trying to fix my algorithm, hopefully it'll work!! Thanks Added after 2 hours 5 minutes: |
2008/8/27 05:28 |
| 4 | saigu | In the following line, I think you want '==' instead of '=': if(choice=count) |
2008/8/27 05:28 |
| 5 | zunwang | That helped somewhat, but my algorithm is still wrong. For the 7th prime number its giving me 13861, I guess I just dont see it? Im about ready to throw my computer at the wall! |
2008/8/27 05:28 |
| 6 | wyslnhhh56 | Google "eratosthenes sieve" for an algorithm. Added after 20 minutes: |
2008/8/27 05:28 |
| 7 | anuo2008 | Thanks for all of your help! Only thing is, is that we havent used arrays yet, so I cant use them. And the long identifier, we haven't used that either. I think im just gonna throw in the towel, ive got the pointers to work, so Il try some more, but not too much! Thanks again!!!! |
2008/8/27 05:28 |
| 8 | hualeyan | Your algorithm is puzzling. It doesn't look much like a prime number algorithm. Here's a simple brute-force approach (not very efficient). It tests a number for primeness by checking to see if it's evenly divisible by any integer between 2 and the number's square root: |
2008/8/27 05:28 |
| 9 | netlgc | And if you are not allowed to use math.h (a library for basic mathematical operations) you can use this verion: | 2008/8/27 05:28 |
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