# Program to check a number can be written as a sum of distinct factorial numbers or not in Python

PythonServer Side ProgrammingProgramming

Suppose we have a positive number n, we have to check whether n can be written as the sum of unique positive factorial numbers or not.

So, if the input is like n = 144, then the output will be True, as 4! + 5! = 24 + 120 = 144

To solve this, we will follow these steps −

• fact := 1

• res := a new list

• x := 2

• while fact <= n, do

• insert fact at the end of res

• fact := fact * x

• x := x + 1

• for i in range size of res -1 to 0, decrease by 1, do

• if n >= res[i], then

• n := n - res[i]

• return true when n is same as 0

Let us see the following implementation to get better understanding −

## Example

Live Demo

class Solution:
def solve(self, n):
fact = 1
res = []
x = 2
while fact <= n:
res.append(fact)
fact = fact * x
x += 1
for i in range(len(res)-1,-1,-1):
if n>=res[i]:
n-=res[i]
return n==0
ob = Solution()
print(ob.solve(144))

## Input

144

## Output

True