44 lines
975 B
C
44 lines
975 B
C
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#include <stdio.h>
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#include <math.h>
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/*
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* as per scribblemaniac's explanation:
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* t - number of trials
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* n - character count
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* p - probability
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* condition: >=1 matches
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* formula: t = log(1-p)/log(1-1/32^n)
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* comes from:
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* distribution X~Binomial(t, 1/32^n)
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* P(X>=1)=p
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*/
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const double probs[] = { 0.5, 0.8, 0.9, 0.95, 0.99 };
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const int charcounts[] = { 2, 3, 4, 5, 6, 7 };
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int main(void)
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{
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printf(" |");
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for (int i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
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printf(" %11d%% |",(int)((probs[i]*100)+0.5));
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}
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printf("\n");
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printf("---+");
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for (int i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
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printf("--------------+");
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}
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printf("\n");
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for (int i = 0; i < sizeof(charcounts)/sizeof(charcounts[0]); ++i) {
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printf("%2d |",charcounts[i]);
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for (int j = 0; j < sizeof(probs)/sizeof(probs[0]); ++j) {
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double t = log2(1 - probs[j]) / log2(1 - (1 / pow(32,charcounts[i])));
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printf(" %12.0f |",t);
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}
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printf("\n");
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}
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return 0;
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}
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