Project Euler：Problem 34 Digit factorials

Posted 2020-10-01 wzjhoutai

145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.

Find the sum of all numbers which are equal to the sum of the factorial of their digits.

Note: as 1! = 1 and 2! = 2 are not sums they are not included.

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

vector<int> int_vet(int a)
{
	vector<int> res;
	while (a)
	{
		int tmp = a % 10;
		a /= 10;
		res.push_back(tmp);
	}
	return res;
}

int a[10] = { 0 };
void p()
{
	a[0] = 1;
	a[1] = 1;
	for (int i = 2; i <= 9; i++)
		a[i] = a[i - 1] * i;
}

int main()
{
	p();
	int res = 0;
	for (int i = 3; i < 10000000; i++)
	{
		int count = 0;
		vector<int> num = int_vet(i);
		for (int j = 0; j < num.size(); j++)
			count += a[num[j]];
		if (count == i)
			res += count;
	}
	cout << res << endl;

	system("pause");
	return 0;
}