C: Store a list of ints in Array [closed] - c

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What i'm trying to solve here is print a list of prime numbers into an array. I'm kinda fresh to C and the following code is what I have so far, it does not seem to accomplish what I am looking for which a list of prime numbers.
#inlude <stdio.h>
int main(void) {
int i, j, arr[40]
for (i=2; i<40; i++){
for (j=1; j<i; j++) {
if (i%j == 0){
arr[i] = 0;
}
else
arr[i] = i;
}
printf("%d\n", arr[i]);
}
}
This code prints a list 0 instead of primes

Answer 1

try this
#include <stdio.h>
#include <string.h>
int main(void) {
int i, j, arr[40]; // you forgot ';' here
int flg =0; // use an additional flag
for (i=2; i<40; i++)
{
for (j=2; j<i; j++) // don't start from j=1? every number is divisable by 1
{
if (i%j == 0) flg=1; // flage raises whenever divisor found
}
if(flg == 0) arr[i]=i; // no divisor ==> prime number
else arr[i] =0; // there are divisors ==> not prime number
flg = 0; // reset flag to use in next iteration, next number
printf("%d\n", arr[i]);
}
}

Answer 2

It seems you posted code which is not original one. It contains many syntax error.
correct first it.
#inlude <stdio.h> must be #include <stdio.h>
put ; after int i, j, arr[40]
Array index must start with 0 but here you initialize array with i=2.
Also use of two for loop is looks bad codding style instead you can use one function which return the status of number if it's prime number or not. like
#include <stdio.h>
int prime(int n){
int j;
for (j=2;j<=n/2;j++)
if((n%j)==0)
return 0;
return 1;
}
void main(){
int i,p,index, arr[40];
for (i=2;index=0,i<=40;i++,index++)
{
p=prime(i);
if(p==1)
arr[index]=i;
else
arr[index]=0;
printf ("%d\n", arr[index]);
}
}

Answer 3

This might be what you want:
#include <stdio.h>
int main(void) {
int i, j, arr[40]={0};
for (i=2; i<40; i++){
for (j=2; j<i; j++) {
if (i%j == 0){
arr[i] = 0;
break;
}
arr[i] = i;
}
}
for(i = 1; i < 40; i++ )
printf("%d\n", arr[i]);
}

Answer 4

First of all, the code you've given doesn't compile. You've written inlude instead of include on the first line, and your declaration of i, j, and arr needs a ; at the end of the line.
With that taken care of, the code compiles, but it doesn't produce 0s - it produces
0
3
4
5
6
...
etc. Your inner loop sets arr[i] at every iteration, so your printf will only see what it was set to that last time through the loop. The last time through the loop, you had j=i-1, which will only satisfy your if when i = 2 (so j = 1)
To fix this you need to do two things:
Break out of the inner loop the first time you find a divisor, to make sure you don't overwrite the 0 that you write when you do find a divisor.
Start the inner loop from j=2 instead of j=1. Remember 1 is a divisor for primes (as well as every other integer), so if you start the loop from 1, all of the numbers will fail your test