Range Sum Query Immutable - Leetcode 303 - Python 

A trick I like to use for the prefix array is to subtract left and add nums[left] instead of going one position over so we don't have to worry about boundary check, for example: prefix[right] - prefix[left] + nums[left]

Great as usual.

2:00 Why O(n^2)? O(n^2) is the time complexity of finding pairs. Intuitively the time complexity is greater to find every subarray

thank you

Amazing!

what if left = 0, right = 0; -2 + (-2)

You wrote left > 0 then but as index , left can be 0 to indicate first index