Problem URL: Sum of even numbers after queries

We will first calculate the sum of all even values. Then we follow the problem instruction, calculate the even sum after modifying the value according the query, then update the even sum and append it to our result. Finally after iterating through all the queries, we return our result.

class Solution:
    def sumEvenAfterQueries(self, nums: List[int], queries: List[List[int]]) -> List[int]:
        evenSum = sum([num for num in nums if num % 2 == 0])
        res = []
        for val, idx in queries:
            if nums[idx] % 2 == 0:
                evenSum -= nums[idx]

            nums[idx] += val

            if nums[idx] % 2 == 0:
                evenSum += nums[idx]

            res.append(evenSum)
        return res

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