Day09 - Recursion 3 (Python 3)
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# Day09 - Recursion 3 (Python 3)

• Objective
• Today, we’re learning and practicing an algorithmic concept called Recursion. Check out the Tutorial tab for learning materials and an instructional video!
• Recursive Method for Calculating Factorial
• Write a factorial function that takes a positive integer, as a parameter and prints the result of N (N factorial).
• Note: If you fail to use recursion or fail to name your recursive function factorial or Factorial,N you will get a score of .

• Input Format

• A single integer,N (the argument to pass to factorial).
• Constraints
• 2 <= N <= 12
• Your submission must contain a recursive function named factorial.
• Output Format
• Print a single integer denoting .

#### 문제풀이

• 팩토리얼 함수를 만들라는건데, python은 팩토리얼이 함수가 math에 있음
```1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 import math import os import random import re import sys # Complete the factorial function below. def factorial(n): return math.factorial(n) if __name__ == '__main__': fptr = open(os.environ['OUTPUT_PATH'], 'w') n = int(input()) result = factorial(n) fptr.write(str(result) + '\n') fptr.close() ```
```1 2 3 4 5 6 # 손으로 한번 풀어보기 def factorial(n): num = 1 for i in range(1,n+1): num *= i return num ```
```1 math.factorial(3) ```
```1 6 ```
```1 2 3 # 재귀함수로 해보기 def factorial_re(n): return n * factorial_re(n-1) if n > 1 else 1 ```
```1 factorial_re(3) ```
```1 6 ```
```1 ```