2025-2026 오성고_공동교육_정보과학 Day 2

algo2_formula.py

def main():
  n = int(input("숫자를 입력하세요: "))
  sum_alternating_formula(n)
  
def sum_alternating_formula(n):
    if n % 2 == 0:
        return n // 2
    else:
        return -(n + 1) // 2

if __name__ == "__main__":
  main()

algo2_loop.py

def main():
  n = int(input("숫자를 입력하세요: "))
  sum_alternating_loop(n)
  
def sum_alternating_loop(n):
    total = 0
    for i in range(1, n + 1):
        if i % 2 == 0:   # 짝수는 +
            total += i
        else:            # 홀수는 -
            total -= i
    return total

if __name__ == "__main__":
  main()

algo2_pythonic.py

def main():
  n = int(input("숫자를 입력하세요: "))
  sum_alternating_pythonic(n)
  
def sum_alternating_pythonic(n):
    return sum((-i if i % 2 == 1 else i) for i in range(1, n + 1))

if __name__ == "__main__":
  main()