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9570419
data
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2012-03-05T16:43:28.300
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2012-03-05T16:43:28.300
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<pre><code>#include <windows.h> #include <stdio.h> #include <stdlib.h> struct prime_list_t { long n; struct prime_list_t *next; }; void add_prime_list_t(struct prime_list_t** list, long n); void free_prime_list_t(struct prime_list_t** list); long count_prime_list_t(struct prime_list_t* list); long last_prime_list_t(struct prime_list_t* list); /* if one of the primes in list divides n, is not a prime */ int is_prime(struct prime_list_t* pl, long n) { struct prime_list_t* p; if(pl == NULL) { abort(); } p = pl; while(p != NULL) { if(n % p->n == 0) { return 1; } p = p->next; } return 0; } int main() { struct prime_list_t* pl = NULL; struct prime_list_t* p; long n_up = 2000000; long long p_sum = 0; long ppr; int done; /* add first prime number */ add_prime_list_t(&pl, 2); /* from now on add to this list up to the number of items */ done = 0; do { /* get the last prime plus one */ ppr = last_prime_list_t(pl) + 1; while(is_prime(pl, ppr) != 0) { ppr++; if(ppr >= n_up) { /* hit the upper limit */ done = 1; break; } } if(done) { break; } /* ppr is prime */ add_prime_list_t(&pl, ppr); /* display status */ printf("%ld numbers largest prime %ld\r", count_prime_list_t(pl), last_prime_list_t(pl)); } while(!done); p = pl; p_sum = 0; while(p) { // printf("%d ", p->n); p_sum += p->n; p = p->next; } printf("\nsum: %I64d\n", p_sum); free_prime_list_t(&pl); return 0; } void add_prime_list_t(struct prime_list_t** list, long n) { struct prime_list_t* node; if(list == NULL) { abort(); } node = (struct prime_list_t*)malloc(sizeof(struct prime_list_t)); if(node == NULL) { abort(); } node->n = n; node->next = NULL; if(*list == NULL) { *list = node; } else { struct prime_list_t* p; p = *list; while(p->next != NULL) { p = p->next; } p->next = node; } } void free_prime_list_t(struct prime_list_t** list) { struct prime_list_t* node; if(list == NULL) { return; } node = *list; while(node != NULL) { struct prime_list_t* p; p = node; node = node->next; free(p); } *list = NULL; } long count_prime_list_t(struct prime_list_t* list) { long c; struct prime_list_t* p; for(p = list, c = 0; p != NULL; p = p->next, c++) ; return c; } long last_prime_list_t(struct prime_list_t* list) { long n; struct prime_list_t* p; n = 0; p = list; while(p->next != NULL) { p = p->next; } return p->n; } </code></pre> <p>And this would be the output:</p> <pre><code>$kpwr 148933 numbers largest prime 1999993 sum: 142913828922 $ </code></pre>
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1. PONeed help optimizing algorithm - sum of all prime numbers under two million
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1. USCristian Amarie
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