1413: [蓝桥杯]阶乘计算

Posted 2021-06-17 幽殇默

http://oj.ecustacm.cn/problem.php?id=1413

#include<cstdio>
#include<iostream>
#include<vector>
using namespace std;
vector<int> mul(vector<int>A,int b)
{
	int t=0;
	vector<int> C;
	for(int i=0;i<A.size()||t;i++)
	{
		if(i<A.size()) t+=A[i]*b;
		C.push_back(t%10);
		t/=10;
	}
	while(C.size()>1&&C.back()==0) C.pop_back();
	return C;
}
int main(void) 
{
	int n; cin>>n;
	vector<int> ans; ans.push_back(1);
	for(int i=2;i<=n;i++) ans=mul(ans,i);
	for(int i=ans.size()-1;i>=0;i--) cout<<ans[i];
	cout<<endl;
	return 0;
}