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NNTP-Posting-Date: Tue, 13 Dec 2011 20:52:11 -0600
Message-ID: <4EE80F5B.6116@mindspring.com>
Date: Tue, 13 Dec 2011 21:52:11 -0500
From: pete <pfiland@mindspring.com>
Reply-To: pfiland@mindspring.com
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Subject: Re: Toughest Probability Question
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.c:14595

Peter Nilsson wrote:
> 
> > pete wrote:
> > I had it right the first time,
> > but I rewrote the whole thing anyway.
> > ...
> > #define YEAR                365  /* 366 */
> 
> To nitpick, this is limiting people to those only born in non
> leap years, or those only born in leap years. The general figure
> is somewhere in between...
> 
>   #include <stdio.h>
> 
>   double P2(int f29, int oth, int n)
>   {
>     double p = 0;
>     if (n == 0) return 1;
>     if (oth < 365)
>       p += (303. / 400 + 97. / 400 * 365 / 366)
>          * (365 - oth) / 365 * P2(f29, oth + 1, n - 1);
>     if (f29 < 1)
>       p += 97. / 400 * 1 / 366 * P2(f29 + 1, oth, n - 1);
>     return p;
>   }
> 
>   double P(int n) { return P2(0, 0, n); }
> 
>   int main(void)
>   {
>     int n = 0;
>     double p;
> 
>     do {
>       p = P(++n);
>       printf("%3d: %7.3f%%\n", n, 100 * (1 - p));
>     }  while (1 - p < .5);
> 
>     return 0;
>   }

I was wondering about how to deal with that.

-- 
pete