Successive prime differences: Difference between revisions
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</pre>
=={{header|C}}==
<lang c>#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#define PRIME_COUNT 100000
int64_t PRIMES[PRIME_COUNT];
size_t primeSize = 0;
bool isPrime(int n) {
size_t i = 0;
for (i = 0; i < primeSize; i++) {
int64_t p = PRIMES[i];
if (n == p) {
return true;
}
if (n % p == 0) {
return false;
}
if (p * p > n) {
break;
}
}
return true;
}
void initialize() {
int i;
PRIMES[primeSize++] = 2;
PRIMES[primeSize++] = 3;
PRIMES[primeSize++] = 5;
PRIMES[primeSize++] = 7;
PRIMES[primeSize++] = 11;
PRIMES[primeSize++] = 13;
PRIMES[primeSize++] = 17;
PRIMES[primeSize++] = 19;
for (i = 21; primeSize < PRIME_COUNT;) {
if (isPrime(i)) {
PRIMES[primeSize++] = i;
}
i += 2;
if (primeSize < PRIME_COUNT && isPrime(i)) {
PRIMES[primeSize++] = i;
}
i += 2;
}
}
void diff1(size_t diff) {
int64_t pm0, pm1;
int64_t fg1 = 0, fg2 = 0, lg1 = 0, lg2 = 0;
size_t pos, count = 0;
if (diff == 0) {
return;
}
pm0 = PRIMES[0];
for (pos = 1; pos < PRIME_COUNT; pos++) {
pm1 = pm0;
pm0 = PRIMES[pos];
if (pm0 > 1000000) {
break;
}
if (pm0 - pm1 == diff) {
count++;
if (fg1 == 0) {
fg1 = pm1;
fg2 = pm0;
}
lg1 = pm1;
lg2 = pm0;
}
}
printf("%ld|%d|%lld %lld|%lld %lld|\n", diff, count, fg1, fg2, lg1, lg2);
}
void diff2(size_t d0, size_t d1) {
int64_t pm0, pm1, pm2;
int64_t fg1 = 0, fg2, fg3, lg1, lg2, lg3;
size_t pos, count = 0;
if (d0 == 0 || d1 == 0) {
return;
}
pm1 = PRIMES[0];
pm0 = PRIMES[1];
for (pos = 2; pos < PRIME_COUNT; pos++) {
pm2 = pm1;
pm1 = pm0;
pm0 = PRIMES[pos];
if (pm0 > 1000000) {
break;
}
if (pm1 - pm2 == d0 && pm0 - pm1 == d1) {
count++;
if (fg1 == 0) {
fg1 = pm2;
fg2 = pm1;
fg3 = pm0;
}
lg1 = pm2;
lg2 = pm1;
lg3 = pm0;
}
}
printf("%d %d|%d|%lld %lld %lld|%lld %lld %lld|\n", d0, d1, count, fg1, fg2, fg3, lg1, lg2, lg3);
}
void diff3(size_t d0, size_t d1, size_t d2) {
int64_t pm0, pm1, pm2, pm3;
int64_t fg1 = 0, fg2, fg3, fg4, lg1, lg2, lg3, lg4;
size_t pos, count = 0;
if (d0 == 0 || d1 == 0 || d2 == 0) {
return;
}
pm2 = PRIMES[0];
pm1 = PRIMES[1];
pm0 = PRIMES[2];
for (pos = 3; pos < PRIME_COUNT; pos++) {
pm3 = pm2;
pm2 = pm1;
pm1 = pm0;
pm0 = PRIMES[pos];
if (pm0 > 1000000) {
break;
}
if (pm2 - pm3 == d0 && pm1 - pm2 == d1 && pm0 - pm1 == d2) {
count++;
if (fg1 == 0) {
fg1 = pm3;
fg2 = pm2;
fg3 = pm1;
fg4 = pm0;
}
lg1 = pm3;
lg2 = pm2;
lg3 = pm1;
lg4 = pm0;
}
}
printf("%d %d %d|%d|%lld %lld %lld %lld|%lld %lld %lld %lld|\n", d0, d1, d2, count, fg1, fg2, fg3, fg4, lg1, lg2, lg3, lg4);
}
int main() {
initialize();
printf("differences|count|first group|last group\n");
diff1(2);
diff1(1);
diff2(2, 2);
diff2(2, 4);
diff2(4, 2);
diff3(6, 4, 2);
return 0;
}</lang>
{{out}}
<pre>differences|count|first group|last group
2|8169|3 5|999959 999961|
1|1|2 3|2 3|
2 2|1|3 5 7|3 5 7|
2 4|1393|5 7 11|999431 999433 999437|
4 2|1444|7 11 13|997807 997811 997813|
6 4 2|306|31 37 41 43|997141 997147 997151 997153|</pre>
=={{header|C sharp}}==
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