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mkp224o/calcest.c

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1.0 KiB

#include <stdio.h>
#include <stddef.h>
#include <math.h>
/*
* as per scribblemaniac's explanation:
* t - number of trials
* n - character count
* p - probability
* condition: >=1 matches
* formula: t = log(1-p)/log(1-1/32^n)
* comes from:
* distribution X~Binomial(t, 1/32^n)
* P(X>=1)=p
*/
const double probs[] = { 0.5, 0.8, 0.9, 0.95, 0.99 };
const int charcounts[] = { 2, 3, 4, 5, 6, 7, 8, 9, 10 };
int main(int argc,char **argv)
{
// TODO
(void) argc;
(void) argv;
printf(" |");
for (size_t i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
printf(" %15d%% |",(int)((probs[i]*100)+0.5));
}
printf("\n");
printf("---+");
for (size_t i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
printf("------------------+");
}
printf("\n");
for (size_t i = 0; i < sizeof(charcounts)/sizeof(charcounts[0]); ++i) {
printf("%2d |",charcounts[i]);
for (size_t j = 0; j < sizeof(probs)/sizeof(probs[0]); ++j) {
double t = log2(1 - probs[j]) / log2(1 - (1 / pow(32,charcounts[i])));
printf(" %16.0f |",t);
}
printf("\n");
}
return 0;
}