int factorial(int x) { int fac = 1; for (int i=2; i<=x; i++) fac *= i; return fac; }
Also, with this function defined, you can use two macros for calculating combinations & permutations:
#define nCr(n, r) (factorial(n) / factorial(n-r) / factorial(r)) #define nPr(n, r) (factorial(n) / factorial(n-r))