LeetCode 2718: Sum of Matrix After Queries Solution

Master LeetCode problem 2718 (Sum of Matrix After Queries), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2718. Sum of Matrix After Queries

Medium

Array Hash Table

Problem Explanation

Explanation:

To solve this problem, we can iterate through each query and update the matrix based on the type of query (row or column update). We can keep track of the sum of the matrix elements after each update and return it at the end.

Here are the steps:

Initialize a 2D matrix of size n x n filled with zeros.
Iterate through each query:
- For type 0 query, update the row with the given index to the specified value.
- For type 1 query, update the column with the given index to the specified value.
- Update the sum of the matrix elements after each query.
Return the final sum of the matrix.

Time complexity: O(n + queries.length)
Space complexity: O(n^2)

Solution Code

class Solution {
    public int sumMatrixAfterQueries(int n, int[][] queries) {
        int[][] matrix = new int[n][n];
        int sum = 0;

        for (int[] query : queries) {
            int type = query[0];
            int index = query[1];
            int val = query[2];

            if (type == 0) {
                for (int j = 0; j < n; j++) {
                    matrix[index][j] = val;
                    sum += val - matrix[index][j];
                }
            } else {
                for (int i = 0; i < n; i++) {
                    matrix[i][index] = val;
                    sum += val - matrix[i][index];
                }
            }
        }

        return sum;
    }
}

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