#238. Product of Array Except Self

Author: papilo-cloud

Prefix_Sum/product_except_self.py

@@ -0,0 +1,43 @@
+# Given an integer array nums, return an array answer such that answer[i] is equal
+# to the product of all the elements of nums except nums[i].
+
+# The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
+
+# You must write an algorithm that runs in O(n) time and without using the division 
+# operation.
+
+ 
+
+# Example 1:
+
+# Input: nums = [1,2,3,4]
+# Output: [24,12,8,6]
+# Example 2:
+
+# Input: nums = [-1,1,0,-3,3]
+# Output: [0,0,9,0,0]
+ 
+
+# Constraints:
+
+# 2 <= nums.length <= 105
+# -30 <= nums[i] <= 30
+# The product of any prefix or suffix of nums is guaranteed to fit in a 32-bit integer.
+ 
+
+# Follow up: Can you solve the problem in O(1) extra space complexity? (The output array
+# does not count as extra space for space complexity analysis.)
+
+
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]: # type: ignore
+        ln = len(nums)
+        result = [1]*ln
+        for i in range(1,ln):
+            result[i] = result[i - 1] * nums[i - 1]
+
+        suffix = 1
+        for i in range(ln-1, -1, -1):
+            result[i] *= suffix
+            suffix *= nums[i]
+        return result