求C(m,n)，即n!/(m!*(n-m)!)，结果对1000000007取模。
需要解决伪溢出问题，最高效率的算法是什么。
#include "math.h"
typedef unsigned int uint32;
uint32 C(uint32 m, uint32 n)
{
double res = 0;
uint32 i, ires;
for (i = n-m+1; i <= n; i++) res += log(i);
for (i = 2; i <= m; i++) res -= log(i);
res = exp(res);
ires = (uint32) res;
if ((uint32)(res + 0.5) != ires ) ires++;
return ires % 1000000007;
}
int main()
{
printf("C(2,3) = %d C(2, 10) = %d C(3, 1000)= %d\n",
C(2,3), C(2, 10), C(3, 1000));
return 0;
}
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