C语言计算分段函数

/*
革启博客，程序袁欢，袁欢的博客，袁欢博客
版本：vs2019社区版
功能：计算分段函数*/
#include
double factorial(int a)
{
	int i;
	double factorial_Value = 1.0;
	for (i = 1; i < a; i++)
	{
		factorial_Value = factorial_Value * i;
	}
	return factorial_Value;
}
void main()
{
	int m = 0, n = 0;
	double factorial_m = 0;
	double factorial_n = 0;
	double factorial_mn = 0;
	double P_mn = 0.0;
	printf("请输入两个参数的值：\n");
	printf("m=");
	scanf_s("%d", &m);
	printf("n=");
	scanf_s("%d", &n);
	if (m > n)
	{
		factorial_m = factorial(m);
		factorial_n = factorial(n);
		factorial_mn = factorial(m - n);
		if (0 == factorial_n || 0 == factorial_mn)
		{
			printf("错误，0不能作为除数！\n");
		}
		else
		{
			P_mn = factorial_m / (factorial_n * factorial_mn);
		}
	}
	else
	{
		P_mn = 0;
	}
	printf("计算结果为：");
	printf("P_mn=%f\n", P_mn);
}