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Problem34.java
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Problem34.java
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/*
* Prompt: Find the sum of all numbers which are equal to the sum of the factorial of their digits.
*
* Execute: javac Problem34.java; java Problem34; rm Problem34.class
*
* Answer: 40730
*/
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
public class Problem34 {
static Map<Integer, Integer> factorials = new HashMap<Integer, Integer>();
public static void main(String[] args) {
int sum = 0;
for (int i = 3; i < 50000; i++) {
int[] digits = getDigits(i);
int sumOfFactorialOfDigits = 0;
for (int d : digits) {
sumOfFactorialOfDigits += getFactorial(d);
}
if (i == sumOfFactorialOfDigits) {
sum += i;
}
}
System.out.println(sum);
}
static int[] getDigits(int n) {
ArrayList<Integer> digits = new ArrayList<Integer>();
while (n > 0) {
digits.add(n % 10);
n /= 10;
}
int[] dig = new int[digits.size()];
for (int i = 0; i < digits.size(); i++) {
dig[i] = digits.get(i);
}
return dig;
}
static int getFactorial(int n) {
Integer f = factorials.get(n);
if (f == null) {
f = factorial(n);
factorials.put(n, f);
}
return f;
}
static int factorial(int n) {
int f = 1;
for (int i = n; i > 0; i--) {
f *= i;
}
return f;
}
}