[c++] N!의 표현법, N!에서 0의 개수

• N!의 표현법

#include <iostream>
#include <vector>
#include <algorithm>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main() {
	//freopen("input.txt", "rt", stdin);
	int n, i, j, tmp;
	scanf("%d", &n);
	std::vector <int> a(n+1);
	for(i=2; i<=n; i++){
		tmp=i;
		j=2;
		while(1){
			if(tmp%j==0){
				a[j]++;
				tmp=tmp/j;
			}
			else {
				j++;
			}
			if(tmp==1) break;
		}
	}
	printf("%d! = ", n);
	for(i=2; i<=n; i++){
		if(a[i]!=0) printf("%d ", a[i]);
	}
	return 0;
}

 

• N!에서 0의 개수

#include <iostream>
#include <vector>
#include <algorithm>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
int main() {
	//freopen("input.txt", "rt", stdin);
	int n, i, j, tmp=1, cnt1=0, cnt2=0;
	scanf("%d", &n);
	for(i=2; i<=n; i++){
		tmp=i;
		j=2;
		while(1){
			if(tmp%j==0){
				if(j==2) cnt1++;
				if(j==5) cnt2++;
				tmp=tmp/j;
			}
			else j++;
			if(tmp==1) break;
		}
	}
	if(cnt1<cnt2) printf("%d", cnt1);
	if(cnt1>cnt2) printf("%d", cnt2);
}