[c language] PTA 7-48 find the number of combinations

This question requires the preparation of procedures , According to the formula Cnm​=n!​/(n−m)!m! Calculate from n Take out... Of the different elements m Elements （m≤n） The combination number of .

It is recommended to define and call functions fact(n) Calculation n!, among n The type is int, The function type is double.

Input format :

Enter two positive integers on one line m and n（m≤n）, Space off .

Output format :

By format “result = Calculation result of combination number ” Output . The results are as follows double Within the scope of type .

sample input :

2 7

No blank lines at the end

sample output :

result = 21

No blank lines at the end

Listen to the questions , Order one double fact（int n）

#include<stdio.h>
double fact(int n);
int main(){
	int n,m;
	scanf("%d %d",&m,&n);
	
	double ans;
	ans=fact(n)/(fact(m)*fact(n-m));
	printf("result = %.0f",ans); 
	
	return 0;
}
double fact(int n){
	int i;
	double f=1.0;
	for(i=2;i<=n;i++){
		f*=i;
	}
	return f;
}

Be careful ：

①fact Return value f, Number of combinations output ans Must be double type , Otherwise, the answer will be wrong （ Why? ...

② Convert a double value to int Data loss occurs when type