Day09 - Recursion 3 (Python 3)

• URL : https://www.hackerrank.com/challenges/30-recursion/problem

• 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
• Task
  • 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

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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()

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# 손으로 한번 풀어보기
def factorial(n):
    num = 1
    for i in range(1,n+1):
        num *= i
    return num

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math.factorial(3)

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# 재귀함수로 해보기
def factorial_re(n):
    return n * factorial_re(n-1) if n > 1 else 1

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factorial_re(3)

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6

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