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CykuTW/C: Primes Table

Last active November 6, 2016 09:42
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C: Primes Table
//run on Microsoft Visual Studio 2015 Express
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define SIZE 1000001
unsigned char table[SIZE];
int main(void) {
clock_t t1, t2;
int i, j, n;
printf("Pleas enter an integer between 2 and 1,000,000\n");
scanf("%d", &n);
//start timer
t1 = clock();
//initialize
table[0] = table[1] = 0;
for (i = 0; i <= n; i++)
table[i] = 1;
//create table
for (i = 2; i <= n; i++)
if (table[i])
for (j = 2; j*i <= n; j++)
table[j*i] = 0;
//output result
for (i = 2; i <= n; i++)
if (table[i])
printf("%d\n", i);
//stop timer
t2 = clock();
printf("execution time: %lf s\n", (t2 - t1) / (double)(CLOCKS_PER_SEC));
system("PAUSE");
}
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