三国杀-周泰不屈的概率计算

翻n张不死的概率如下：
1 100.0000%
2 92.3077%
3 78.1065%
4 60.0819%
5 41.5952%
6 25.5970%
7 13.7830%
8 6.3614%
9 2.4467%
10 0.7528%
11 0.1737%
12 0.0267%
13 0.0021%



#include <stdio.h>
#include <math.h>
double getn_die( int n )
{
    if( n <= 0 ) return 0;
    const int c = 13;
    double x = n/double(c);
    for( int i = 0 ; i < n-1 ; i ++ )
        x *= (c-i-1)/double(c);
    return x;
}
double getn_nodie( int n )
{
    double x = 0;
    for( int i = 0 ; i <= n ; i ++ )
        x += getn_die(i);
    return 1-x;
}
int main()
{
    int i,c = 13;
    double d = 0;
    printf( "no die\n");
    for( i = 0 ; i < c ; i ++ )
    {
        d = getn_nodie( i );
        printf( "%d %.4f%%\n", i+1,d*100.0 );
    }
    return 0;
}