Difference of Squares in Python

문제

참고할 자료와 개념

• Learn Python in Y Minutes
• python 공식 문서 Tutorial : 4.3 range
• python 공식 문서 내장 함수 : sum
• python 공식 문서 내장 함수 : map
• python 공식 문서 Tutorial : 4.8.6. 람다 표현식
• python 공식 문서 Tutorial : 5.1.3. List Comprehensions

풀이된 예제

명령형

def square_of_sum(number):
	total = 0
	for n in range(1, number + 1):
		total += n
	return total * total

def sum_of_squares(number):
	result = 0
	for n in range(1, number + 1):
		result += n * n
	return result

def difference_of_squares(number):
	return square_of_sum(number) - sum_of_squares(number)

pythonic iterartor

def square_of_sum(number):
	return sum(range(1, number + 1)) ** 2

def sum_of_squares(number):
	return sum(n * n for n in range(1, number + 1))

def difference_of_squares(number):
	return square_of_sum(number) - sum_of_squares(number)

map과 lambda

def square_of_sum(number):
	return sum(range(1, number + 1)) ** 2

def sum_of_squares(number):
	return sum(map(lambda n: n * n, range(1, number + 1)))

def difference_of_squares(number):
	return square_of_sum(number) - sum_of_squares(number)

수학

• 수학방 : 등차수열의 합 공식
• 수학방 : 자연수 거듭제곱의 합 공식, 유도

def square_of_sum(number):
	return (n * (n + 1) / 2) ** 2

def sum_of_squares(number):
	return n * (n + 1) * (2 * n + 1) / 6

def difference_of_squares(number):
	return square_of_sum(number) - sum_of_squares(number)