c++实现1000以内的阶乘

#include <iostream>
#include <vector>
const int MAX_NUM = 1000000;
using namespace std;
//自写大数阶乘
void testBig(int n,vector<int> &v) {
	//计算阶乘1~n
	for (int i = 2; i <= n; i++) {
		int flag = 0;//表示进位
		for (vector<int>::iterator it = v.begin(); it != v.end();it++) {
			int isMax = *it * i + flag;//将数组vector定为10w进制
			*it = isMax % MAX_NUM;
			flag = isMax / MAX_NUM;
		}
		if (flag != 0) {
			v.push_back(flag);//若进位标志不为0，则加入数组尾部
		}
	}
}

//输出
void testPrintBig(vector<int>& v) {
	int flag = 0;//标志位，最高位不能为0
	for (vector<int>::reverse_iterator it = v.rbegin(); it != v.rend();it++) {
		vector<int> v1(6);
		int num = 1;//除位标志，每次乘10
		for (vector<int>::iterator itJ = v1.begin(); itJ !=v1.end(); itJ++) {
			*itJ = *it / num % 10;
			num *= 10;
		}
		for (vector<int>::reverse_iterator itJ = v1.rbegin(); itJ != v1.rend();itJ++) {
			if (!flag) {
				if (*itJ == 0) {
					continue;
				}
				else {
					flag = 1;
				}
			}
			if (flag) {
				cout << *itJ;
			}
		} 
	}
}

//主函数
int main()
{
	int n = 0;
	vector<int> v;
	v.push_back(1);
	cout << "请输入您希望计算的阶乘: ";
	cin >> n;
	testBig(n, v);
	testPrintBig(v);
	system("pause");
	return 0;
}