題目要求

We have an array A of integers, and an array queries of queries.

For the i-th query val = queries[i][0], index = queries[i][1], we add val to A[index]. Then, the answer to the i-th query is the sum of the even values of A.

(Here, the given index = queries[i][1] is a 0-based index, and each query permanently modifies the array A

Return the answer to all queries. Your answer array should have answer[i] as the answer to the i-th query.

題目分析及思路

題目給出一個整數數組A和一個query數組，query數組的每一個元素是一個列表，該列表由兩個整數組成，分別對應一個值和一個A索引。要求把該值加到該索引對應的A數組的值，然後將A數組中的偶數求和。最後返回所有query對應的結果。首先對A中所有偶數求和，之後遍歷query數組，判斷某索引對應A中的值在加值前後的奇偶性。

python代碼

class Solution:

def sumEvenAfterQueries(self, A: ‘List[int]‘, queries: ‘List[List[int]]‘) -> ‘List[int]‘:

res = []

s = sum([i for i in A if i % 2 == 0])

for v, i in queries:

if A[i] % 2 == 0:

s -= A[i]

A[i] += v

if A[i] % 2 == 0:

s += A[i]

res.append(s)

return res

LeetCode 985 Sum of Even Numbers After Queries 解題報告