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238. Product of Array Except Self
Medium
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
numsis 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.)
Solution
# @param {Integer[]} nums
# @return {Integer[]}
def product_except_self(nums)
product = 1
ans = Array.new(nums.length, 1)
nums.each {|num| product *= num}
nums.each_with_index do |num, i|
if num != 0
ans[i] = product / num
else
p = 1
nums.each_with_index {|n, j| p *= n unless j == i}
ans[i] = p
end
end
ans
end