Problem URL: Find triangular sum of an array

This problem is basically reverse pascal's triangle. For the ith element of one level, we can calculate it from the i and i+1 th element from the previous level and mod the result by 10. After each level, we will remove the last element of that level. We will continue, until there is only one element left in the level, then return that value.

class Solution:
    def triangularSum(self, nums: List[int]) -> int:
        n = len(nums)
        while n > 1:
            for i in range(n-1):
                nums[i] = (nums[i] + nums[i+1]) % 10
            nums.pop()
            n -= 1
        return nums[0]

Time Complexity: O(n^2)
Space Complexity: O(1)