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Project Euler 34–Digit factorials

By Wu Yudong on August 20, 2018

Digit factorials

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.

145是个有趣的数，因为1! + 4! + 5! = 1 + 24 + 120 = 145。

//（Problem 34）Digit factorials
// Completed on Thu, 25 Jul 2013, 16:11
// Language: C
//
// 版权所有（C）wu yudong
// 博客地址：http://www.wuyudong.com

#include<stdio.h>
#include<math.h>
#include<stdbool.h>

int factorial(int n)			//阶乘函数
{
if (n == 1 || n == 0)
return 1;
else
return n * factorial(n - 1);
}

bool judge(int n)	//判断一个整数是否符合题意的函数
{
char s[10];
sprintf(s, "%d", n);
int len = strlen(s);
int sum = 0;
for (int i = 0; i < len; i++) {
sum += factorial(s[i] - '0');
}
if (n == sum)
return true;
else
return false;
}

int main()
{
int sum = 0;
for (int i = 3; i < 1000000; i++) {
if (judge(i))
sum += i;
}
printf("%d\n", sum);
return 0;
}


Completed on Thu, 25 Jul 2013, 23:11