https://leetcode.com/problems/sum-of-even-numbers-after-queries/
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.
Example 1:
Input: A = [1,2,3,4], queries = [[1,0],[-3,1],[-4,0],[2,3]]
Output: [8,6,2,4]
Explanation:
At the beginning, the array is [1,2,3,4].
After adding 1 to A[0], the array is [2,2,3,4], and the sum of even values is 2 + 2 + 4 = 8.
After adding -3 to A[1], the array is [2,-1,3,4], and the sum of even values is 2 + 4 = 6.
After adding -4 to A[0], the array is [-2,-1,3,4], and the sum of even values is -2 + 4 = 2.
After adding 2 to A[3], the array is [-2,-1,3,6], and the sum of even values is -2 + 6 = 4.
Note:
1 <= A.length <= 10000
-10000 <= A[i] <= 10000
1 <= queries.length <= 10000
-10000 <= queries[i][0] <= 10000
0 <= queries[i][1] < A.length
代码:
class Solution {
public:
vector<int> sumEvenAfterQueries(vector<int>& A, vector<vector<int>>& queries) {
int na = A.size(), nq = queries.size();
int sum = 0;
vector<int> ans;
for(int i = 0; i < na; i ++) {
if(A[i] % 2 == 0) sum += A[i];
} for(int i = 0; i < nq; i ++) {
int pos = queries[i][1], val = queries[i][0];
if(A[pos] % 2 == 0) {
if((A[pos] + val) % 2 == 0)
sum += val;
else sum -= A[pos];
} else {
if((A[pos] + val) % 2 == 0)
sum += val + A[pos];
}
A[pos] += val;
ans.push_back(sum);
}
return ans;
}
};