Add Sieve of Eratosthenes

This commit is contained in:
Daniel Grimshaw 2017-10-02 10:40:24 -07:00
parent bb8c41b2de
commit b5b5ec103b

46
primes.c Normal file
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#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
void primes(bool * primeList, int len) {
int i, j;
// Initiallize the list
for (i = 0; i < len; i++) {
primeList[i] = true;
}
primeList[0] = false; // 0 is not prime
primeList[1] = false; // 1 is not prime
for (i = 0; i < len; i++) {
if (primeList[i] == true) {
for (j = i*i; j < len; j = j+i) {
primeList[j] = false;
}
}
}
}
int main(void) {
int size, i;
bool * list;
// Ask for the largest value to check primeness
printf("Maximum value: ");
scanf("%d", &size);
// Allocate list to act as prime mask
list = malloc(sizeof(bool) * size);
// Populate list
primes(list, size);
// Print prime numbers
for (i = 0; i < size; i++) {
if (list[i] == true) {
printf("%d\n", i);
}
}
return 0;
}