题解 | #N的阶乘#

#include<iostream>
#include<vector> 
#include<algorithm>
using namespace std;

vector<int> mul(vector<int> A, int b)
{
	int t = 0;
	int len = A.size(); 
	vector<int>ans;
	for(int i = 0;i < len || t;i++)
	{
		if(i < len) t += A[i] * b;
		ans.push_back(t % 10);
		t /= 10;
	}
	return ans;
}

void print(vector<int> v)
{
	for(int i = 0;i < v.size();i++)
	{
		cout << v[i] ;
	} 
	puts("");
}

int main(void)
{
	int N;
	while(cin >> N)
	{
		vector<int>v;
		v.push_back(1);
		for(int i = 2;i <= N;i++)
		{
			v = mul(v,i);
		}
		reverse(v.begin(),v.end());
		print(v);
	}

	return 0;
}