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#include <stdio.h>
#include <stdlib.h>
#include <math.h>
int n = 1000000;
int *listPrimes(int num){
int i;
int *primes;
int *sieve = (int *) malloc(num * sizeof(int));
//initialize to all 1s (except 0 and 1 which are not prime)
for(i = 2; i < num; i++)
sieve[i] = 1;
for(i = 2; i < ceil(sqrt(num)); i++){
if(sieve[i] == 1){
int j = i * i;
while(j < num){
sieve[j] = 0;
j += i;
}
}
}
//now check which were prime
int s = 0;
primes = (int *) malloc(sizeof(int));
for(i = 2; i < num; i++){
if(sieve[i]){
primes[s] = i;
s++;
primes = (int *) realloc (primes, (s + 1) * sizeof(int));
}
}
return primes;
}
int main(){
int *p = listPrimes(n);
int prime10001 = p[10000];
printf("%d\n", prime10001);
return 0;
}
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