54 lines
1.6 KiB
C
54 lines
1.6 KiB
C
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#include <stdio.h>
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int main()
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{
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int arraySize, i, j, x;
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int numberPrimes = 0;
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printf("Input a positive integer to find all the prime numbers up to and including that number: ");
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scanf("%d", &arraySize);
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int n = arraySize / 2;
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int size;
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/* array to start off with that will eventually get
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all the composite numbers removed and the remaining
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ones output to the screen */
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int isPrime[arraySize + 1];
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int TheseArePrime = 0;
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for (i = 0; i < n; ++i)
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{
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isPrime[i] = i;
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}
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for (i = 1; i < n; i++)
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{
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for (j = i; j <= (n - i) / (2 * i + 1); j++)
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{
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isPrime[i + j + 2 * i * j] = 0;/*From this list, remove all
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numbers of the form i + j + 2ij */
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}
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}
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if (arraySize > 2)
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{
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isPrime[TheseArePrime++] = 2;/*this IF statement adds 2 to the output */
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}
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for (i = 1; i < n; i++)
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{
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if (isPrime[i] != 0)
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{
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isPrime[TheseArePrime++] = i * 2 + 1;
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}
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}
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size = sizeof isPrime / sizeof(int);//total size of array/size of array data type
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for (x = 0; x <= size; x++)
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{
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if (isPrime[x] != 0)
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{
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printf("%d \t", isPrime[x]);
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numberPrimes++;// the counter of the number of primes found
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}
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else
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{
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break;
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}
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}
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printf("\nNumber of Primes: %d", numberPrimes);
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return 0;
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}
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