Created
October 20, 2015 08:13
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clucky.c: fast lucky number sieve
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#include <stdio.h> | |
#define QMAX 100000001 | |
// we pretend these are 1 indexed, gross... | |
int seq[QMAX]; | |
int count[QMAX]; | |
// could replace this with a no-op and print the whole thing at the end | |
void emit_result(int n){ | |
printf("%d\n", n); | |
} | |
void sieving(){ | |
int n = 5; | |
seq[1] = 1; | |
seq[2] = 3; | |
emit_result(seq[1]); | |
emit_result(seq[2]); | |
count[2] = 0; | |
int idx = 3; | |
while(idx < QMAX){ | |
int pos = 2; | |
for(;;){ | |
if(pos >= idx || seq[pos] > idx){ | |
// we've run out of numbers to check | |
// number is safe | |
emit_result(n); | |
seq[idx] = n; | |
count[idx] = 0; | |
n += 2; | |
idx++; | |
break; | |
} else if(count[pos] == 0){ | |
// this has been killed by seq[pos] | |
// move to the next n | |
n += 2; | |
count[pos] = seq[pos]-1; | |
break; | |
} | |
count[pos]--; | |
pos++; | |
} | |
} | |
} | |
int main(){ | |
sieving(); | |
} |
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