solved product-of-array-except-self.

Author: sangbeenmoon

product-of-array-except-self/sangbeenmoon.py

@@ -0,0 +1,26 @@
+# idea
+# 1. left[i] = left[0] * left[1] * ... * left[i-1]
+# 2. right[i] = right[i+1] * right[i+2] * ... * right[n-1]
+# 3. answer[i] = left[i-1] * right[i+1]
+
+# time : O(n)
+# space : O(n)
+
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        left = [1] * len(nums)
+        left[0] = nums[0]
+        for i in range(1, len(nums)):
+            left[i] = left[i-1] * nums[i]
+
+        right = [1] * len(nums)
+        right[len(nums) - 1] = nums[len(nums) - 1]
+        for i in range(len(nums) - 2, 0, -1):
+            right[i] = right[i+1] * nums[i]
+        
+        answer = []
+        answer.append(right[1])
+        for i in range(1, len(nums) - 1):
+            answer.append(left[i-1] * right[i+1])
+        answer.append(left[len(nums) - 2])
+        return answer