54 lines
1.1 KiB
C
54 lines
1.1 KiB
C
/* The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
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*
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* Find the sum of all the primes below two million.*/
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#define _POSIX_C_SOURCE 199309L
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include "projecteuler.h"
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#define N 2000000
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int main(int argc, char **argv)
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{
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int i;
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int *primes;
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long int sum = 0;
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double elapsed;
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struct timespec start, end;
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clock_gettime(CLOCK_MONOTONIC, &start);
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/* Use the function in projecteuler.c implementing the
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* Sieve of Eratosthenes algorithm to generate primes.*/
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if((primes = sieve(N)) == NULL)
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{
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fprintf(stderr, "Error! Sieve function returned NULL\n");
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return 1;
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}
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/* Sum all the primes.*/
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for(i = 0; i < N; i++)
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{
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if(primes[i])
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{
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sum += i;
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}
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}
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free(primes);
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clock_gettime(CLOCK_MONOTONIC, &end);
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elapsed = (end.tv_sec - start.tv_sec) + (double)(end.tv_nsec - start.tv_nsec) / 1000000000;
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printf("Project Euler, Problem 10\n");
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printf("Answer: %ld\n", sum);
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printf("Elapsed time: %.9lf seconds\n", elapsed);
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return 0;
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}
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