238. Product of Array Except Self

원문: https://doljae.tistory.com/69

[Product of Array Except Self - LeetCode

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leetcode.com](https://leetcode.com/problems/product-of-array-except-self/)

1. 숫자 기준 왼쪽, 오른쪽 곱배열을 구한 뒤 곱배열을 곱해서 반환

from typing import *

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        answer = []
        temp1 = [1]
        for i in range(1, len(nums)):
            temp1.append(temp1[-1] * nums[i - 1])
        temp2 = [1]
        for i in range(len(nums) - 1, 0, -1):
            temp2.append(temp2[-1] * nums[i])
        for i in range(len(temp1)):
            answer.append(temp1[i] * temp2[::-1][i])
        return answer

2. 동일한 원리, 최적화

from typing import *

class Solution:
    def productExceptSelf(self, nums: List[int]) -> List[int]:
        answer = [1]
        for i in range(1, len(nums)):
            answer.append(answer[-1] * nums[i - 1])
        temp = 1
        for i in range(len(nums) - 1, -1, -1):
            answer[i] = answer[i] * temp
            temp *= nums[i]
        return answer